Counting each Mii class and PT's 'mons separately, we are up to 35 characters confirmed (9 64 vets, 5 Melee vets, 10 Brawl vets, 11 newcomers), with 14 characters circa Brawl unconfirmed (there's also the 5 characters that jumped ship post-Melee, but this number won't count towards the total). Assuming everyone from Brawl were to immediately come back today, we would be at 49. Factor out certain characters that have actual fear of being cut (Snake, Squirtle and Ivysaur), that would give us 45-46, give or take Ice Climbers.
Now, for some unnecessary bonus credit; If we take our current roster size of 35 and add in the remaining characters from that rumored leak (Shulk, Chrom, Chorus), that would obviously be 38, 52 if we add the remaining Brawl hopefuls, back to 48-49 if we subtract Snake, Squirtle, Ivysaur and potentially Ice Climbers.
For some fun, let's assume the 5 Melee cuts actually got a new lease on Smash. The totals for that would be 40 with the current roster, 54 with everyone from Brawl back, 50-51 by subtracting the potential Brawl cuts, and back up to 53-54 by adding the "leaked" characters on top of that.
Hope you all enjoyed this little lesson, because I sure didn't.
DISCLAIMER: While Squirtle and Ivysaur are the most likely cuts, I added Snake into that list because as a 3rd Party character, he has (in a certain manner of speaking) the least number of bargaining chips for returning. In addition, the reason why I only counted Ice Climbers halfway is because even though it's been said that the 3DS would have trouble getting them in, it's never in a light that suggests they are a guaranteed cut. Finally, even as I say all of this, I don't want to see any characters cut from the game, especially Ivysaur since she was the main PT mon I liked to used. Not to mention I too still hope some lost Melee characters come back, most of all Pichu <yes i'd put Pichu in before Mewtwo and Roy, wanna fight about it?>