Sega has changed the release date for Sonic Generations. But in the good direction, not the bad one.
The 3DS360 (that's a combination of 3DS, PS3, and Xbox 360) title will now be released on December 1. The previous date was December 8.
In their Japanese form, the HD and portable versions have different names. PS3 and 360 owners should look for Sonic Generations: Shiro no Jikuu. 3DS owners should look for Sonic Generations: Ao no Bouken.