It looks like Sonic Generations might be coming to the 3DS, after reading this list of upcoming 3DS games that was printed yesterday:

Generations3DS gamestop

Look near the bottom.

So, as some have asked, the answer to the question: "Is Sonic Generations coming to a Nintendo game system," the answer is yes as far as we know. Now, for the Wii? We don't know. It's being assumed a whole other Sonic game will be released for the Wii this year, but there's still a possibility that Sonic Generations will come to the Wii. Most likely not, but there's still a possibility.

Stay tuned for more updates.