To be honest, I don't believe he really needs to.
Sure, it's nice to see big, surprising names. But shock and awe isn't the only thing that makes a good character.
That's true, but still, I don't think Sakurai can make a Smash without that shock factor anymore.
He gave us Mega Man, Pac-Man, Sonic, Ryu, Cloud and Bayonetta. In the same game!
He gave us the possibility to see these popular icons of past and present battle against some of Nintendo's best...
Dreams that wandered in gamers' minds for a long time came true with that game!
How could he start over without having such incredible third parties in its roster?
Sure, there's always DLC, but I don't see how he could make things as simple as they were before...