I think new racial models will definitely be a major feature of the next expansion, and they'll show at least a few of them in the reveal cinematic next Blizzcon.
I don't think a 4th spec for all classes is going to happen. Adding another 10 specs would make the game even harder to balance than it is now. Not all players would welcome having a healing or tanking option for their pure dps class either.
As WoW's popularity has shown some signs of waning, there's pressure on them to deliver more stuff with each expansion. I'd guess we'll be getting a new class and new character models for the oldest races. Possibly another new race or two on top of that.
Also Ghostcrawler said
this when asked if pure dps classes are here to stay. Seems like an unlikely answer if they were doing away with pures next expansion: