Trailer
YouTube - Street fighter 4 trailer
Getting a bit of an Okami vibe... I don't think this indicates that this will not be a 2D fighter, so 2D fans don't get too upset. It's just a trailer.

SF4 really has a high bar to reach for, not only from SF3 but because of the competition that has since come out. KOF is a perennial rival, but the Guilty Gear franchise started after SF3 was first released. Not that I think GG or KOF is better than Street Fighter (despite my choice of avatar), but there's a lot more serious competition out there now.