I doubt it will be Super Mario Bros Mii. I mean it's cool and all, but I think they just made a small sample of it just to show at E3 last year. I'm' hoping for a 3D platformer that isn't Galaxy 3 or Sunshine 2. I want it to be something like Galaxy, Sunshine, and Super Mario 64, but I don't want sequels.
It's a new Super Mario 2 game that they're likely to release a few short months after the WiiU comes out. It may be for both WiiU and 3DS but I'm not quit sure yet.