Speaking to French games magazine IG, Hideo Kojima seemed to confirm that Metal Gear Sold 5 is in development. It is believed that it is being made on the new FOX Engine.
“About Metal Gear Solid 5, I can tell you two things. There will be much question of infiltration, espionage, and convincing people to give you ‘a favor’ like in the last Metal Gear Solid,” he said. “I liked the idea of social interactions in Deus Ex: Human Revolution, but we will see. And if I say more, the female ninja public relations officer, who is behind the door, will carve me up into pieces. So it’s better that we meet again when the time comes to talk about Metal Gear Solid 5.”
IG later confirmed that the quote are genuine, while further adding, “Metal Gear Rising: Revengeance never claimed to be a Metal Gear Solid. This is not a game about our beloved Solid Snake. It is a spinoff that tries something different. We have not yet finished with Solid Snake, despite the fact that I wanted to let him die at the end of Guns of the Patriots.”
Source: CVG {link no longer active}