Yes, proof. Right here:
http://sonic.sega.jp/sonic/Press the characters button. (Which is conviniently English AND Japananese!) You know the rest.
Since his little selectable is smaller, I'm betting that he isn't a story character, but definately some other mode of some sort. (Try saying that five times fast, lol!) He will definately AT LEAST be in 2P mode or something.
Unfortunately, he is not playable in the demo, but oh well. They're still working on 'im. And Shadow. And Silver. @_@
The demo was great, so you guys know. Sonic was the only one, as I just mentioned, but the gameplay is NOT with the 'Heroes and Shadow engine! (THANK GOD!!!) You don't go rushing off of cliffs because you just SLIGHTLY pressed a bit to a side, no. It's basically SADX's engine, with minor enhancements, such as:
Homing onto a rail, thank God.
The havok engine. (Seriously, boxes tumble and fall down cliffs and stuff, it's awesome.)
The camera angle barely ever fails.
I've only homing-attacked a cliff once, and that was probably my fault. What I was aiming at was behind the camera...
mrgreen