Nintendo Power magazine has a big cover feature on Bioware's eagerly awaited Sonic RPG for the Nintendo DS, which is now titled Sonic Chronicles: The Dark Brotherhood. There are 11 playable characters, with Sonic, Tails, Amy, Knuckles, Rouge, Shadow and Big the Cat being the ones already known. Eggman/Robotnik will be in it, but not as the main villain (supposedly).
Bioware, if you don't already know, are the talented creators of Baldur's Gate, Star Wars: Knights of the Old Republic and Mass Effect amongst others, and are well known for never having made a game that was less than a classic - Sonic's in very capable hands with them.
For further details, visit N-Europe.com, who have more info from the mag and a link to scans in their forums.
Source: N-Europe