While I think a villains trailer could happen, and it would definately be smart on Sakurai's part, What I see as more likely is that we get another Smash bros. direct in August, revealing mewtwo sometime in the direct outside of a trailer, though still showing the splash like zss and shiek, and showing some gameplay, and maybe the same for ganondorf if he has a new moveset, maybe wario and/or metaknight too, then the long awaited Ridley trailer at the end of the direct, with just Ridley, and King K Rool as a secret character. That seems like the most likely fate for our villains to me.