Speaking to 1UP, Payton insisted that whilst MGS4 was the closing chapter for the series’ leading man, Solid Snake, there’s plenty more in the game’s universe that can be explored – including the back-story to main villain Big Boss.
"There are some misunderstandings that this is the final Metal Gear game. But it's really the final chapter of the Solid Snake story. That's all. There is still a lot of room for filling in the gaps as far as Big Boss is concerned.
"I'm happy we could wrap up Snake's story in MGS4 because it gets to the point where if we continue on with Metal Gear Solid 5 with more Solid Snake adventures, we'll get to the point where the game has absolutely no basis in reality.
“I do like the idea that this character has had four or five big missions and then that's when it ended, rather than have 20 missions where there's no chance in hell a secret agent could ever survive. He's had four or five really big missions, and that seems a little more realistic to me."