[Update: Microsoft has commented on the listing, stating that it is "completely inaccurate and not provided by 343 or Microsoft."
A pre-order description for the new Halo game (which may or may not be Halo 5) was spotted on the Microsoft Store, and it gives us a tiny glimpse into the sort of thing Master Chief will be dealing with on the Xbox One. It appears as if ol' Johnny boy is in possession of a "mysterious" data chip, as he deals with a situation that involves the hunting of all sentient life in the galaxy. Yep, sounds like a typical day for the Chief.
The Microsoft Store also list a placeholder date of 12/31/14, which is probably bogus, but possibly indicates a 2014 release. Either way, I've seen a lot of jaded Halo fans since ODST, and I hope the new Halo can really mix things up to bring people back in again.
Halo [Microsoft Store]