Well I'll give my reaction to some of these new rumors, and again, these are only rumors.
I am just going to spell this out how it is. People have seen printed in GW rulebooks 25% max characters and 25% lord 25% hero. I think many GW stores will be basing their demonstrations on 25% lord 25% hero. Make of that what you will.
This will allow some of the old character combos, so I think it is fine. As long as 25% core is still required.
Allied forces will not get a % allocation. However, rules for using allied forced (i.e. an updated allied forces chart) are in the rulebook.
Allies are now split into 3 groups:
Forces of Order: High Elves, Wood Elves, Lizardmen, Empire, Dwarfs and Brettonia
Forces of Destruction: Chaos of any kind, Skaven, Greenskins, Dark Elves (edit. Vampire Counts may go here).
Neutral: Ogres and Tomb Kings
The allies rules are intended to be used by more than 2 players. You are not supposed to use more than one armybook in your army.
Allies are allowed to use the other army General’s leadership, but cause panic in units of the other army if they are forced to flee. If an allied unit is forced to flee through another ally from a different group, the stationary unit counts as dangerous terrain. I.e. High Elves flee through Warriors of Chaos.
Cool. Now team battles will actually carry some fluff value. Using the other general's leadership is cool too. I approve.
You may measure distances whenever you want.
Oh no! The world is ending! Actually this isn't as bad as it seems. Remember that charge distance will have a random factor to it. As with many of the changes being made, the purpose seems to be to speed the game up a little bit.
Charging.
Rumoured to be:
Infantry M1-M6 = Basic Movement value + 2D6
Fast Attack M7+ (Cavalry and fliers) = Basic Movement value + 3D6 use 2 highest)
+1CR for charging. -Avian (more likely)
Flyers take a bit of a nerf, but they had it coming to be honest. Dragons may be not quite so common.
Fliers
Move 10 " and march 20 ". They ignore terrain whilst moving. While fleeing or pursuing, they use their ground movement. (note: the ground movement part may not be entirely correct)
Wow, fliers now must march to go 20". This is another nerf that will help reduce the dominance of flyers. Seems fair enough.
Marching.
Movement distance as normal. When there's an enemy within 8", the unit has to pass a leadership test to march. Not sure how this applies to Dwarfs.
Hmm, random march blocking? So march blocking won't always work. This will make march blocking more likely to happen against enemies far to the flank, who have no support from the general's leadership. I think this will de-emphasize march blocking as an effective strategy.
Reforming
Units may reform once, but may neither move nor shoot the same turn. If the unit has a musician, it may move afterwards, or shoot. (Note: I'm pretty sure I'm missing some details on that one.)
This could make ranked units a bit more flexible. This is in keeping with the direction the game is heading.
Generating Power and Dispel Dice
Power dice aren’t generated by the number of spellcasters. The amount of dice is decided by 2D6. The active player gets the total as power dice and the other player the highest throw as dispel dice (throw 3+5, = 8 PD and 5 DD). (confirmed)
Channeling (confirmed that it exists)
Each wizard may roll a D6 and generate an additional power dice on a roll of 6.
Each enemy wizard may roll a D6 and generate an additional dispel dice on a roll of 6.
You may not channel while fleeing, off the board or when you suffer from stupidity..
Maximum Power and Dispel Dice
The maximum number of power or dispel dice you may have at any time is 12. This includes any power/dispel dice generated by special rules, spells and/or magic items.
This is an interesting change, and should prevent magic spam. It also puts a cap on the Focused Rumination. Roll up a 12 for your power dice and the Focused Rumination does nothing. But your magic phase is maxed out in that case. Roll up a 10 instead and you can still max out your magic phase if the Slann casts 2 spells. "Capping" your magic phase with Focused Rumination is actually better than rolling up 12 on your initial 2d6... since your opponent will be less likely to have 6 dispel dice.
Casting Spells
To cast a spell, roll 1 to 6 Power dice and add your caster's power level. EG: A Slann casts fireball and uses 2D6. He rolls a 3 and a 4 - score of 7. He than adds his Power Level of 4, which results in a total roll of 11.
Not bad, this will be the new advantage to using a high level caster. Fewer dice to produce a higher casting value. I could see the same rule applying to mages trying to dispel enemy magic.
Miscasting
Here is where I think we need a lot more information.
It is rumoured that miscasts are entirely gone, but are replaced by a combined irresistible force/ miscast table effectively:
When you roll a double 6 the spell is cast with irresistible force, but the Caster has to roll on the "lost control" chart, which is devastating, and far more worse than the current miscast table.
Lost Control Chart
Roll of 1: This has been confirmed as being even worse than number 4… Which (pure speculation) may involve every model in the unit taking a hit, this was something I actually heard a while back, but it could be worse than this.
Roll of 4: The wizard is sucked into the warp and the large template is centred over him. S10 hits for something (could be the centre model, meaning S5 for the rest?).
Looks like Becalming Cogitation gets left at home now. I'd rather the enemy get blitzed by a miscast and suffer the effects of the irresistable spell. Also it raises a question about Cupped Hands of the Old Ones... Does this mean the spell goes off but the miscast is transferred? Or does the miscast effect the enemy wizard who then gets to cast his own spell? The Lizardmen errata will need to clear this up.
Bound spells
Bound spells are cast like normal spells now, but instead of your caster's power level, you add the level of the magic item. (Not 100 % sure on this one)
How would this effect the Jag Charm on a saurus? Maybe it'll go back to just being something that always works and isn't actually a spell?
Spells are now categorized. There are: Missiles, Curses, Buffs, Direct Damage and Power Whirl spells.
Missiles: Require Line of Sight and may not be cast into close combat.
Curses: Modify enemy stats and/or equipment
Buffs: Support your own troops
Direct damage: Spells that use templates or apply to the whole target unit.
Power whirls: Apply to all of the battlefield or move across the table.!?
Each lore has an additional effect. For example:
Lore of Shadows: After the wizard successfully casts a spell, he may switch places with another friendly character of the same unit type.
Lore of Death: For each wound caused by lore of death spells, roll a D6. On a roll of 5+ you are granted an additional power dice.
Lore of Fire: If the enemy suffered a from a fire lore spell earlier this magic phase, the caster is granted a Bonus of +3 when casting a fire spell upon the same target.
Lore of Metal: Direct damage spells from the lore of metal have no strength value. Instead the unmodified armour save of the target is the required roll to wound. This causes flaming attacks and ignores armour saves.
This should clear up spells a whole lot, breaking them up into discrete categories. Reminds me a lot of when I did the magic review... maybe they stole the idea?

Fire will be good for wiping out single big units, and this may be something you see more of in 8th edition.. Empire hordes perhaps?
True Line of sight
Units draw true line of sight. You are considered in cover when shot at through another unit, granting a -1 or -2 penalty on to hit rolls. Note that someone else has said this is more likely as well.
So skirmish screens will now just reduce the effectiveness of shooting against what they are screening. It also completely changes the game in a ton of ways. Will the "Large Target" rule even still exist? Maybe all "monsters" will be +1 to shoot at. I think GW is cooking up a scheme to sell more laser pointers. I don't like this rumor, as I think the sight rules are simple enough with the square bases.
Infantry models in the second rank can fight, with a maximum of 1A per model. - Avian/Harry. Great weapons can only be used in one rank. – Godless.
This is only for models fighting to the front. Units charged in the flank or rear only fight in 1 rank, but being charged in the flank or rear will not stop units fighting in multiple ranks to the front.
Most special rules apply as normal. however... Whatever combination of weapons/ special rules/ spells/ whatever, infantry can only ever attack with 1 attack per model in the second and subsequent ranks.
The great weapon thing is not bad, won't hurt LM at all. Kroxigors are monstrous infantry, so it won't hit them. The 1 rank to flank or rear will be really good for us if it is true. This will let our skrox units have a big impact on the game, and will be better for flanking the big blocks. Now we just need to move the kroxigors back to the third rank so two ranks of skinks get to attack on the charge. It also seems to confirm that spear saurus will be getting only 1 attack from the second rank. I will be modeling up some HW+SH guys it seems!
One Save.
A model can always take an armour save. They can then take either a ward save or a regeneration save.
Hmm, well I guess Nurgle Daemons with regen and their 5+ ward will be hit by this. Other than that, saves seem to be as normal. It prevents things from stacking ward with regen, so I guess it tones down powergaming a little bit.
Crush them!
Monstrous Cavalry and Monstrous Infantry are granted 1 bonus attack with the "always strikes last" special rule, at base strength
Destroy them!
Larger Creatures and Monsters do D6 attacks instead of 1 attack for crush them.
Ancient Stegadons seem really good, D6 extra str 6 attacks! This seems like a way to compensate monsters a little bit for losing their ability to deny ranks.
Magic Resistance
This has been changed to improve an existing Ward Save, or to grant a Ward Save to magic.
Magic Resistance 1 = +1 Ward Save against Magic. For a unit without a ward save this is 6+
Magic Resistance 2 = +2 Ward Save against Magic. For a unit without a ward save this is 5+
Magic Resistance 3 = +3 Ward Save against Magic. For a unit without a ward save this is 4+
For things that already have a Ward Save, Flesh Hounds for instance, they have a 5+ Ward save already, and MR(3). This gives them a 5+ save against shooting/ combat, and a 2+ Ward Save against magic.
Regeneration
Regeneration will come in several types. The Slanns ability for example will grant him Regeneration (3+), while there is a mundane magic item that grants regeneration (6+).
So magic resistance can only help defend against damaging spells now. This is not bad, and seems to be in keeping with capping power/dispel dice. The slann regeneration seems kind of pointless if you now can't combine it with your ward save... I guess regeneration is just becoming another kind of ward save.
Lots and lots of changes coming. True line of sight is the one that bothers me.. I think it will actually slow the game down rather than expedite things. It will also create needless arguments and force us to buy laser pointers. Everything else sounds fine to me.