Maybe you saw it coming, maybe you didn't, but even though Metal Gear Solid 4: Guns of the Patriots is not yet out on stores, it seems that series creator Hideo Kojima is already thinking about Metal Gear Solid 5. Here's what Kojima told Famitsu (translation courtesy of Kotaku):

I gotta start thinking about MGS5... Even though, well, Snake's story ends in MGS4. ...About MGS5, that would be something that Kojima Productions would have to make, I think.

Of course, we've reported before that MGS4 will only bring closure to Snake and is not necessarily the end of the whole series. Kojima also didn't  mention what capacity he'll be serving in IF a Metal Gear Solid 5 (Metal Gear Sasaki? Metal Gear Raiden?) does get made.