It seems that despite Hideo Kojima’s protestations, there will be another Metal Gear Solid, presumably starring Snake in some fashion. This was confirmed by Game Informer, and could explain why there was another producer change with Metal Gear Solid: Rising. More details will be in the upcoming PlayStation UK magazine.
It was suspected Metal Gear Solid 5 would be announced at this past E3 for PC, Xbox 360 and PlayStation 3.