Masahiro Sakurai talked about the controls, game mechanics, and cameos in the upcoming Super Smash Bros. games for the 3DS and Wii U:
“The GameCube controller is not the only way to control Smash Bros., so we will look into ways that fits the Wii U.”
“The game system itself is complete, so we don’t want to make it 3D or introduce complicated controls just for the sake of it. However, I am thinking of ways we can introduce a slightly different, fun experience all the while keeping the usual frantic game play.”
“I think Snake and Sonic joining were fantastic. It made many fans happy, and it broadened the Smash Bros arena. However, introducing more non-Nintendo characters willy-nilly will lose the focus of the game, so I also recognise the need to narrow it down.”
We will just have to wait and see what they come up with for control options on the Wii U. You could just use a Wii U Pro Controller. We may also see some new third-party characters make it into the roster of characters, but expect just a couple.