I could see the Inklings being one of them If Nintendo wants to really push this New IP more.
I could sense 1 more pokemon to be in it. But im not a Pokemon fan soooooo IDK who could it be. But Greninja was a very popular pokemon in X and Y <---- so that could be a reason why he was in it.
I can see W101 to be in it. And if Nintendo wants to do some double Platinum in smash, they can add Bayonetta too .
An anime character would be awesome as well. - Naruto? Luffy?
Pocky Lover Boy!