Today's circulating Internet rumor (no, not that one, the other one) is that Sega and Panovation are on the verge of announcing an online RPG set in the world of Sonic the Hedgehog. There's a little circumstantial evidence out there and no official comment from anybody in charge yet, but that hasn't stopped speculation. You know how these things work.
If this turns out to be true, is there value in an online Sonic RPG? The best thing about the Sonic games are being able to play as Sonic. If there is a MMORPG coming set on Mobius (or Station Square or wherever Sonic spends his time these days) obviously not everyone can be Sonic, so what is the fun in that? Who wants to spend time in a virtual world where the central figure of the established mythology is not under your control? It'd be like playing a Legend of Zelda MMORPG set in Hyrule, but you cannot play as Link.
I'd imagine this will end up as something like The Matrix Online MMORPG in which Morpheus and the other (surviving) characters from the films are controlled by the company that's running the show (note that Sega is behind The Matrix Online). I can see Sega setting up an environment where Sonic and his freedom fighters wage war against Dr. Robotnik and his badniks. Players can choose a side and become their own unique character: Sonic gets animals, while Robotnik gets the robots.
And it's probably worth mentioning that this isn't the first time rumors have gone around regarding a Sonic RPG. It almost happened in 1992 when Sega planned to replace the characters in the Japanese version of the Sega CD RPG Popful Mail with Sonic spin-off characters such as Sonic's unseen sister. Fans revolted, however, and Sister Sonic was dead before it left the drawing board.