A Japenese direct has confirmed that there will be a new Mario and Sonic game! It will be coming to the WiiU and the 3DS.
Another thing that is known is that more characters are going to be playable, and they are:
- Rouge the Bat
- Zazz (I'm not joking)
- Diddy Kong
- Jet the Hawk
- Espio (I think I saw his flag there)
There were trailers of this game, but the user has removed them.
EDIT: Nintendo Direct announcement! You can see some new characters:
Looks like two new sports are there, Rugby ( I think it's called that) (WiiU) and Golf (3DS)
That's all the information we could find, stay tuned for more updates!