This opens up more than a few questions. First, will the game be a retail release or an Xbox Live Arcade port of an older title? The fact that it's already rated means it must be complete, and we find it hard to believe that a new retail title would have remained under wraps this long. Besides, the ESRB has provided us with plenty of good XBLA leads lately.
Note that the ESRB recently rated the unannounced EA Replay 2. We'll have more information on this exciting rumor as it becomes available. Thanks to lxi for spotting this first.