I think it will end up a mixture of 2D specific levels and 3D that occassionaly goes into 2D during certain parts, as you've seen in recent Sonic console games. I'll agree though, it looks pretty cool.
I dunno, I never really held true to the idea that all recent efforts have been awful Sonic games. Sonic 4 was pretty good. Sonic Colours is the best it has been in some time. This looks to have a combination of both, so I'm pretty happy. But then, I'm not enough of a diehard Sonic fan to complain about things like the physics of Sonic 4, or how his running animation looks weird.