Damn, I just wrote out huge post about character predictions, but it just got erased. I'll try again.
Anyway, based on Famitsu's projected 240 hours to complete single player with all characters, two logical character numbers are 30 and 40:
30 characters = 8 hours per playthrough
40 characters = 6 hours per playthrough
These are the simplest calculations based on the 240 number which is why I'm pointing them out first.
I'm trying to have realistic expectations for this game. The increase in characters from the original to Melee was huge, but the hardware jump from GCN to Wii is nowhere near as great, which is why I'm being more conservative in predicting about 30 playable characters. Another factor which lowers this number is that i believe Sakurai wanted to do away with clones for the most part.
Another thing, a lot of you are predicting a ton more newcomers to be announced, maybe as many as 10+ more. This would be great, but many of you are forgetting that we've already had 11, 12 if you count ZSS newcomers announced. That's already a pretty big number. As I said, I'm trying to be realistic here and not set myself up for disappointment. If Sakurai completely blows it out of the park with 35+ or even 40, that'd be absolutely insane, but I'm not expecting this at all. With all the stuff he's already crammed into this game, I'm thinking around 30 is more realistic. Then again, Sakurai's surprised us before, so who's to say he won't again.
After doing some calculations, some other possible character numbers are:
32 characters = 7.5 hrs per playthough
34 characters = roughly 7 hours per playthough
37 characters = roughly 6.5 hours per playthrough
So far 23 playable characters have been announced (ZSS and Sheik not counted).
IMO, these characters are pretty much guaranteed:
-Capt Falcon
-Ganondorf
-Luigi
-2 more Pokemon
Here are the "maybe"s
-Falco
-Young Link (cel-shaded or not)
-Another Pokemon
-Mr. Game and Watch
-Another Fire Emblem character
Looking at these, the minimum, not including more newcomers would be 28. So my bet would be 28 plus around 4 or so newcomers.
It really also depends on whether Sakurai is commited to bringing back everyone's favorites, or whether he just wants to do away with clones (Dr. Mario, Falco, Pichu, Fire Emblem, etc.)
If he brings back a good number of them, then we'll see 32ish characters with a few more newcomers, or around 35/36.
Anyway, if you didn't bother reading this, I don't care, I just thought I'd put in my two cents before the game was released. Just my predictions. Sorry for the long ass post.
Summary: My prediction 30-35 characters