Since this thread is the big speculation thread, I'll repost my thoughts from another thread about K Rool, so people know the reasoning behind the demand. Like any character he's got a reason to be in but far too many people brush him off as a dumb choice.
1.Would make up for how DK got the short end of the stick in representation (The infamous 8 versions of the same song issue amongst other things)
2.Another Super Heavyweight to compliment the others (Plus buffs it back up to Brawl having 6 S.Heavies), speaking of
3.The closest thing we'll get to Snake at this rate (Knowing Konami). A Super Heavyweight with a focus on zoning and a strong set of moves is what people feel like K Rool would be like, with stuff like the crown toss, cannonballs, electric and spike traps.
4.A general lack of villains in the game. Without Wolf there's only Bowser, Bowser Jr and Ganon with a bunch of Anti Heros/Anti Villians (Wario, Mewtwo, King Dedede, Meta Knight, Dark Pit).