I would love to help with this project. Not sure if Generations is the right way to go, as Anti Alias said, we might want to focus on getting a good engine working like the previous 3D games first, because, to be honest, I would love a "good" Sonic 06, but a Sonic 06 themed Generations would be so different gameplay wise that it almost seems pointless, we might as well just make a new game all together in that case.
With that said, when the direction has been chosen, I'd love to help, like I said. I have some texture-talent and I've worked some with 3D Environments, so level-designing is something I could at least help with. If we're not too many, I'd love to help clean up the 06 story as well, as I feel there's a damn good time-travel story in there somewhere, just begging to be unearthed.
But like I said, Anti Alias has a good point.