I hope the rumor will be proven false, though, remembering past, it's a very desperate hope. Really, SEGA, why recolor Sonic? Aren't other characters enough? I'm getting tired of playing only Sonic(s) or forms of him. Sonic Adventure was a nice example of various gameplay, except, maybe, fishing. Or even Sonic 3 & Knuckles - having Tails/Knuckles greatly extended the game. Added Tails in Sonic CD port is a good sign.
As for the name, if it's true, Sonic Dimensions can be just a working title, like Sonic Anniversary, later renamed to Sonic Generations.