My unsolicited two cents on the army books: I'm keeping mine, at least for a year. I have two rationalizations.
First, we don't know that Age of Sigmar is the *only* new game coming out. Some rumors suggest AoS is a "gateway" product to entice people into small-scale games, and that a "full-scale" game will appear much later this year. I'm (perhaps naïvely) hopeful that this rumored "full-scale" game will look more like an 8.5E than an AoS.
Second, I also play Dungeons & Dragons, and occasionally homebrew RPG systems that basically amount to the same thing. As a Dungeon Master / Game Master, the sheer amount of inspirational art, cartography, and writing (even when that last is sloppy or cheesy) in those books is a marvelous resource. As a simple example, rather than describe a scaly, flying, toothy-monster for twenty minutes, it's way easier to point to the Ripperdactyl picture and say "That. You see that. Except it doesn't have a rider, and its breath smells horrible - probably because of the rotting intestinal tube you spot dangling out the side of its mouth." (Of course, all, or at least most, of that art is out there in Google land easily enough, but if you want to keep the game offline, then the books are superior.) You don't even have to use precise things from the books, but they can definitely inspire other creative thoughts!
Anyway, that's just my plan. If you'd rather sell them for money now, instead of keeping them for a vain hope, then don't let me stop you. I don't know the truth of this new era any better than you!
(Third thought - out of print nerd books look great on a shelf!

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