Today, at GDC ’13, The Phantom Pain/Metal Gear Solid Ground Zeroes has official being called “Metal Gear Solid V”. During the stream, game play videos, trailers, and information regarding the FOX engine were given. There is certainly a lot of information to take in from the footage. That means a whole bunch of speculation. We’re presuming that Psycho Mantis and Revolver Ocelot shows up in some fashion, but we’re only going on what we saw.
We’ll be posting a link for the entire conference when it becomes available.
UPDATE: Contrary to what Kojima announced at GDC, Konami has confirmed that Ground Zeroes is actually still a separate game from Metal Gear Solid V: The Phantom Pain. Details are still hazy on what it is, but I wouldn’t doubt some sort of prequel story or something along those lines. –Source