During the Vocation live event at Tokyo Game Show 2014, it has been confirmed by Kojima that Metal Gear Solid V: The Phantom Pain will release next year, in 2015. This goes for all platforms. Some had hoped the game would launch at the end of this year, but it seems that this is not the case, and fans will have to wait a little longer.
At this point a more precise release date has not been announced yet.
Source: TGS Vocation event, via JunkerHQ