Adriasang reports Sega will launch a demo for Sonic Generations on June 23rd (tomorrow) on both the PlayStation Network and Xbox Live. The site also reports that the single-level demo will be removed from both online stores on July 12th and if already downloaded, will no longer work.
Sony has listed on the PlayStation Europe Blog that the demo is indeed hitting stores tomorrow. That is one region and platform confirmed but wether the demo will also be offered in North America is yet to be confirmed but is likely to happen. Still no word about the Xbox live demo from either region or Japan.
The PlayStation Network is still down in Japan so PlayStation gamers in Japan may be out of luck as there is no evidence showing that PSN will be back soon.