Hideo Kojima has confirmed that Metal Gear Solid 5 is in the works and that it will be built using the Fox Engine. The developer told French magazine IG that he's working on the game and that Solid Snake is in it. According to Eurogamer.fr, "MGS5 will be more of an infiltration game, with characters who can interact, as seen in Deus Ex: Human Revolution."
That's basically the extent of the details we got on the game. Since we know that it uses the Fox Engine though, we can rule out the possibility of seeing the game anytime this console generation. Other than that, all we know is that in the past Kojima said that he'd be interested in having MGS5 set during the invacison of Normandy.
"I had several ideas for a game featuring The Boss and the Cobra Unit during the invasion of Normandy. I then handed these plans over to the team so they could take over and make the game," Kojima said. "I presented my ideas to the team during the summer of 2008. However, simply dropping MGS5 on the younger staff members was a bit heavy and there was resistance to doing it without my involvement."
As we get more details on Metal Gear Solid 5 we'll be sure to give you updates.