Ubisoft's official Asssassin's Creed site reveals a launch date for Assassin's Creed 4: Black Flag by use of some technical wizardry that involves replacing a letter in the URL.
As DarkZero discovered, heading to the official AC4 site for the world premiere trailer, which will launch in four days, and then simply adding a "v" to the end of the url reveals the above image.
The Ubisoft site notes an October 29 release date for AC4 and states it's "also coming to next-gen consoles." Sony announced the PlayStation 4 last week, Microsoft is expected to announce the next Xbox within a few months.