I really hope that the team is like 1.5x bigger than Brawl team because I would like to see 45ish characters because I would be not happy to see some characters being cutting due to not enough times that they have been saying for last 3 games production.
I think Nintendo should give Sakurai three full years to make Smash 4. Keep in mind that development for Brawl began in October 2005 and probably concluded in November or December 2007, giving them two years of development time.
This would mean though that Smash 4's earliest release date would be Q4 2014, but I would be perfectly fine with that.
As long as all 39 characters of Brawl's roster return, Mewtwo and Roy are brought back, and Ridley and Mega Man are added in, I would be perfectly happy with the roster. Characters such as Dixie Kong, Little Mac, K. Rool, and Toad would simply be icing on the cake. Sakurai should really delay the game if there are more characters he wants to get in (I would have been very ecstatic if Mewtwo, Roy, and Dixie Kong had made it into Brawl). A Smash Bros. game only comes ONCE per six or seven years, so he should take as much time as he likes.