We're happy to report that, according to an NGamer interview with Sega Studio USA's Takashi Iizuka, at least the classic gameplay will be intact. Iizuka said that he decided to keep the game concept the same out of consideration for those of us for whom it's been a long eleven-year wait. Not only is the gameplay basically the same, but the composer for the original game is back.
Of course, all of this is very encouraging, but it doesn't eliminate the possibility of Sega pulling a Sonic 360 and releasing a game that is disappointing in surprising new ways. We hate that we have to add the "don't forget, this is Sega" disclaimer, but we do, especially with Sonic Team.