"Dudes, this box art rules!" We would have been satisfied to leave it at that after sharing Fable 3's regal cover art with you, had it not been for the curious stamp at the top: "Only on Xbox 360 & Windows." The label, which denotes "exclusivity" on Microsoft's console and PC, was most recently adhered to THQ's atmospheric first-person shooter, Metro 2033.
Since this official Microsoft-provided art has now been retracted (from Games Press), you're either looking at an elaborate labeling error or an accidental announcement of Fable 3 heading to PC. We'll do our best to be royal pains and keep bugging Microsoft for a proper answer. At the time of writing, neither Microsoft US nor Microsoft UK had responded to our calls.
Update: A Microsoft representative told us, "We have not made any official announcements beyond 'Fable III' for Xbox 360 at this time," and offered to forward additional information "as it becomes available."