It looks like Sonic Generations will be receiving the special edition treatment. At least, it appears that way in the UK, where retailer GAME has posted PS3 and Xbox 360 listings for Sonic Generations: Special Edition.
The PS3 version includes a bonus "Casino Night" level, which recreates the pinball-themed level from Sonic the Hedgehog 2. In addition to the bonus level, the Xbox 360 version includes a Super Sonic Avatar outfit and a dashboard theme.
We've contacted Sega to see if the Special Edition is speeding its way to America as well.