In a recent issue of Games TM, Masahiro Sakurai explains why you may not see any fighting characters appearing in the Super Smash Bros. game for Wii U and 3DS. He says that, unfortunately, these characters already fight like another somewhere in the game, so it’s not a good fit. So far, Mega Man is the only new third-party character to make his debut within the universe as Sakurai even suggested we treat him as a “special case”, and it doesn’t look like we’ll be getting any others from fighting games in the near future.
“The biggest feature we look at in Smash Bros. is, ‘What does this character bring to Smash Bros. that other characters don’t?’ If you look at… someone from a fighting game already, and people like fighting with this character, from my point of view, it’s like ‘this guy does what this guy already does. He fills the role that this character already has. So while you may like this character and he’s interesting, that doesn’t really merge well, here.” – Sakurai