I actually agree with Psyborg that I'm not necessarily keen on the idea of it being just Sonic.
I mean, I certainly don't like the way Sega vomits out new characters for every game, but it is nice just to change things up a bit. Knuckles and Tails in S3&K, for example, and Blaze in Rush, only have subtle differences so it's not annoying like having to do hunting levels or anything (assuming you don't like them, I personally don't mind them so much), but you still have to play the game in some different ways.
Also, one character is fucking boring from a storyline POV, not to mention character interaction (yeah, bite me, I'm interested in storyline and characters, even though Sega have the storytelling abilities of an epileptic frog).
As for that video...um, there wasn't much there. And what was didn't look great, to be honest. Reggie was talking about how Sonic is now "completely under your control", but it looked like a goddamn rail-shooter. We'll just see, though.