There is one character that I would love to see in the next Smash: Mega Man. I've wanted Mega Man in smash since the first game was released on the N64. Some people may not remember the GameShark, or that you could write your own codes for the GameShark. I spent a lot of time trying to make Samus blue so that I could pretend she was Mega Man.
With the addition of Snake & Sonic to Brawl, I thought we had a chance of getting Mega Man. Sonic was the mascot of Nintendo's long time rival, Sega, and Snake (with the exception of Twin Snakes and a GBC came) had been a Sony exclusive for several years. If Nintendo could bag those 2 characters, it seemed possible, nay, likely that they could add Capcom's blue bomber.
Given that last year was Mega Man's 25th anniversary, and that Capcom celebrated it by not releasing a new game, cancelling the two games they had in development for him, and did not release a collection of any sort, it seems like Capcom should let Nintendo use Mega Man. Capcom didn't even use him in Marvel vs Capcom 3! Capcom doesn't seem to care about their mascot, so let Nintendo put him to good use. Smash games live forever. Immortalize Mega Man.