I don't really know what to expect. I've had 2 games that I want Nintendo to make: Mario Paintball Arena and a mature Starfox meets Turok type game (Starfox Dinosaur Hunter). Both of those are over the shoulder FPS in my mind. But they don't involve new characters...
My guess would be an inovative 3D platformer title. Games live Gex, Crash, Glover, Banjo Kazooie, etc come to mind. Something new and exciting, something with good humor, something with imaginative characters. This would be a new game world, not just another Mario.
I would also like to see Nintendo try a sandbox game, or maybe something like a prince of persia or assassin's creed.
Then again, an entirely new experience is possibly on the way.