Users on the Sonic Stadium forums have captured what appears to be leaked (and temporary) box art for two upcoming Sega games, one of which features a logo for the new, recently teased Sonic game. It's set to be called "Generations," which fits in with early domain registrations allegedly done by Sega, as well the trailer's depiction of both the original (see: potbellied) and redesigned hedgehog hero.
A second leaked cover also indicates that Sega is working on Mario & Sonic at the London 2012 Olympic Games for Wii. No surprise there, as the first Mario and Sonic sold over five million copies and its winter-based sequel did another six and a half million. We've contacted Sega for comment.