http://www.techradar.com/news/metal-gear-solid-6-release-date-trailers-and-news

Metal Gear Solid is in a strange place. Its creator, Hideo Kojima, no longer works at Konami, but the publisher still owns the rights to the series. Konami is already hard at work developing Metal Gear Survive, a spin-off that takes place at some point between Metal Gear Solid V: Ground Zeroes and Metal Gear Solid V: The Phantom Pain and fills it out into a co-op zombie survival game. 

Clearly, Konami is happy to keep developing the series so it’s only a matter of time until it sets its sights on a more full-blooded sequel, a Metal Gear Solid 6.