Update: The magazine scan has been revealed and it is apparently a HOAX.
ICEknight @ The GHZ translated a Spanish interview Shakidna posted at Sonic Cult:
C. Doriga:We’re almost running out of time, one last question: Are you going to include SEGA’s mascot, Sonic The Hedgehog?
M. Sakurai:Well… That’s a tough question, I’ll tell you that Sonic’s already in the game, but we’re still waiting for a last confirmation from SEGA. Due to the proximity of the game’s release, SEGA’s deadline to submit their confirmation is the 26th this month, and in that date the official site will be updated about the inclusion o not of SEGA’s mascot in the game. I’m personally crossing my fingers.