Well, as it turns out, that video was indeed a fake. The trailer, which states that Halo 4’s release date is later this year in November, has officially been debunked by Microsoft.
This is actually a fake,” a Microsoft spokesperson said. “We haven’t officially announced the release date yet but stay tuned.
To be honest, the video (which can be seen here) is obviously a little fishy in itself. While I don’t doubt that Halo 4 will be out later this year most likely in the fourth quarter, it won’t be on the 21st. For that news, let’s wait until a real leak happens or when Microsoft officially releases it.
Source: Game Informer