Metal Gear Solid V: The Phantom Pain. That tells you most of what you need to know right there--the next in Hideo Kojima's cinematic stealth action series will be a combination of what we've seen of Metal Gear Solid: Ground Zeroes and The Phantom Pain.
A GDC panel on the tech behind the game--Kojima Productions' vaunted Fox Engine--kicked off with the news, along with a new trailer said to be running live from a PC build. It looks like Snake has spent nine years in a coma before the game begins, significantly weakening him.
His hospitalization ends with the linear scenes depicted in the Phantom Pain trailer, eventually transitioning to the open-world scenarios promised in Ground Zeroes.