[Update: Game Informer's Jim Reilly has tweeted an official response from Microsoft: "This is actaully a fake. We haven't announced the release date yet but stay tuned." Looks like we've got nothing more than a convincing forgery on our hands. The original story follows below.]
A mysterious new teaser has purportedly revealed Halo 4's release date. If the trailer is to be believed, we can expect Master Chief to makes his hotly anticipated return on November 21, 2012.
The video, which claims to showcase Halo 4's cinematics effects through a series of abstract pre-rendered shots, was allegedly uploaded to Halo Waypoint before being pulled by Microsoft. It's hard to tell whether or not it's the real deal, as there's very little that's distinctly Halo about it, save the 343 Industries watermark and closing tag, both of which would be relatively easy to fake.
Still, the production values seem a bit too high for your run of the mill forgery, and the video is remarkably close to the very official concept art teaser released by Microsoft at PAX Prime in August. If it's a fake, it's a fairly well done one.
Provided this is, in fact, a legitimate leak and not a complicated hoax, then odds are good this mirror will be pulled shortly, so watch it while you still can.