5. Who won't make the cut?
If you're a longtime Smash Bros. fan, this outstanding question probably outranks the other four in this list. Not one to be content with simply adding more characters, Sakurai has stated the next Smash Bros. will not feature a larger cast. He cites balance issues and the limitations of the 3DS version as why we won't see more characters than the 36 in Brawl.
Mr. Game & Watch, R.O.B, and Wolf O'Donnel won't make the jump to the Wii U/3DS Smash Bros., if I had to guess. We've already seen four new characters announced—the Villager, Mega Man, the Wii Fit Trainer, and Rosalina—and I would bet Nintendo has a couple more surprise reveals, so quite a few players might be cut. Will we see Solid Snake again, or has he been replaced by Mega Man? What about Pikachu, Jigglypuff, Lucario, and the Pokemon Trainer? Sakurai and his team might want to trim down the overabundance of Pokemon-themed brawlers. I wouldn't put much hope on characters like King Dedede and Ike, either. Sheik and Zero Suit Samus are also missing at this point, even if their counterparts—Zelda and Samus—have been confirmed.
Unfortunately, this is a question that won't be answered until someone inevitably leaks the official character roster sometime in the future.