Well, from Smash Bros to Smash Bros. Melee they added 13 new playable characters
from Smash Bros. Melee to Smash Bros. Brawl they added 11 new playable characters
I think it's safe to expect around 10 to 15 new playable characters on Smash Bros. Wii U
Edit: that... and the fact that they can add even more characters by DLC to boost sales
from Smash Bros. Melee to Smash Bros. Brawl they added 11 new playable characters
I think it's safe to expect around 10 to 15 new playable characters on Smash Bros. Wii U

Edit: that... and the fact that they can add even more characters by DLC to boost sales