Board Thread:Super Smash Bros. Discussion/@comment-25096445-20140624181622/@comment-24383380-20140624183735

In a trailer, a lot of people thought it was Mewtwo, but nope, it was Greninja all along. So, I'm gonna guess that Mewtwo might not return at all.

As for any other Pokemon characters, I think Jigglypuff might return, as it is one of the original 12 characters since the first Super Smash Bros. game.