According to this article, the Sonic Generations will only come to the Wii if the HD version greatly exceeds the expectations. Personally, I think this is a good idea. If Sonic fans love Sonic a lot, they will buy the HD version so the game can come to the Wii. I may have read it wrong, though, so feel free to correct me if I'm wrong.
That's stupid. Not everyone can get the consoles needed to play that. I would think they would allow it regardless of the graphics in hopes to just get more people to buy it.