I think a full Pokémon game in 3D is fairly possible. I mean, as some of you said, they've already made the Pokédex 3D, with all the 649 Pokémon (formes included), and I think these models look really beautiful in the small screen. Furthermore, each one of them has an attack animation -some even have two- and the application isn't that big. Having these, they have to make the overworld in 3D, something they have experienced with in current and past generations, so... it isn't that a big deal, knowing that modeling buildings is not as difficult as modeling living and organic things.
I think is not neccesary to animate EVERY attack of EVERY Pokémon. It's just fine and neat as it is in the Pokédex 3D. Also, it seems to me that making the wild Pokémon walk over the grass and attack you, is not a big plus to the game, as the effort they'd have to put in that can be used in something more... enriching.
Also, having a Pokémon game in full 3D doesn't mean the essence -of art and gameplay- will be lost. We've already seen PBR, PokéPark, even XD and Colloseum, and they're still Pocket Monsters.
So... yes, a Pokémon game in 3D is possible, and I want it.