It’s finally been confirmed by Hideo Kojima via Twitter that Ground Zeroes will in fact be a prologue to Metal Gear Solid V: The Phantom Pain. He also stated that Metal Gear Solid V: The Phantom Pain takes place nine years after the events of Ground Zeroes.

Konami also confirmed with Joystiq that Metal Gear Solid V: The Phantom Pain and Ground Zeroes are in fact separate games, however the length of each game is still in question.

In the same tweet from Mr. Kojima, he mentioned that The Phantom Pain is the “main game”, so Ground Zeroes could merely be an additional add-on ‘prologue’ event, much like Metal Gear Solid 2: Sons of Liberty and its Tanker-Plant / Big Shell incident or Metal Gear Solid 3: Snake Eater and its Virtuous Mission / Operation Snake Eater events.

At this stage, who knows? We shall just have to wait until more details come pouring in, however I personally can never argue with having more Metal Gear in my life!