According to Tssznews.com, the new version of the 3DS Sonic Generations does have a homing attack for Classic Sonic. There was a video a few days ago where this already could be seen. There is no confirmation whether or not you have to gain this move or if it exists in the console version too. My guess is, that if one version has it, all of them do.
In other news, Radical Highway zone (from Sonic Adventure 2) seems to be confirmed for the 3DS version, as is Emerald Coast Zone.