Hideo Kojima is the man behind The Phantom Pain. Not that it's any real surprise.
The man himself has just Tweeted a photo of a video edit suite, and as spotted by those clever people at Neogaf, in the background in very small writing was the file name "TPP_GDC 2013_720p_esrb" - which we are translating as The Phantom Pain, Game Developers Conference, 2013.
So there we go. We knew it all along, but now it is confirmed.