Personally I think that Seraphon are going to be alright with the changes. If anything, GW seems to be pushing hyper-mobility and shooting as the preferred playstyle, and we're already really good at that. It sounds like they are really attempting to balance things better in 3e, so hopefully we'll see less of a difference between the "S-tier" armies and the rest. Of course, they are continuing their tradition of taking good ideas that are unique to certain factions and giving them to everyone else, but I don't think we'll be losing bound spells. I think that we'll just be able to control any bound spell anywhere on the board. And if people start to bring more endless spells, we have ways of countering that pretty easily.
Core battalions seem like a great idea, as do the reactive command abilities in each phase. Since our army is generally swimming in CP, we'll be able to take advantage of those a lot more than many factions. I'm not as enthusiastic about the +/-1 cap on buffs, since every army has ways to get bonuses to hit and to save. It just means that good base warscrolls are now going to be even better, since it's going to be really easy to negate any buffs your opponent puts on their units or debuffs on your own. That rule does really hurt synergy-reliant armies like Seraphon, but at the same time it does negate some of the crazy cheese that some armies are able to do where they can get up to -4 to be hit or drop down to 1+ re-rollable saves...