I'm pretty sure it's going to be a brand new cast, as it always has been for each numerical increment in the series. Of course they'll probably keep the typical carry-overs, Ken, Ryu, Chun-Li, Akuma, etc. I'm actually hoping for a smaller cast this time, I'd like to see them take more time balancing a smaller cast than adding a bunch of new characters into the mix.If it's 3D I'll cry.Arcade is all that matters. The "teaser trailer" for the game featured a short brawl between Ken & Ryu that was done in 3D watercolor-looking art, very much like Okami. However, I highly doubt that it was meant to reflect the actual look or feel of the game, and tend to think it was more focused on letting people know that Street Fighter 4 was definitely coming.
Anyway, I certainly wouldn't be opposed to a weird or traditional watercolor art style, but 3D would totally kill it for me.