Rather than speculate, I have a proposal. Other than the primaries (Mario, Link, Samus, etc), make the rest of the roster brand new fighters.
Let the speculation, arguing, and eventual crushed expectations begin!
Masahiro Sakurai said that the final Super Smash Bros. 4 roster was fully decided two years ago because of development time issues.
Fox and Falco in. Krystal and Wolf out (for now anyway).
A bunch of Smash Bros characters were revealed in huge leak.
Confirmed that more characters beyond those already announced are coming to Smash Bros.
A petition to put Krystal in the next Smash Bros. game.