You didn’t really think Kojima would leave the series behind after the last one, did you? C'mon, son.
Konami has not separately confirmed Metal Gear Solid 5, and it’s possible Kojima is hypothetically speaking about a sequel to Metal Gear Solid 4: Guns of the Patriots, but we’ll have to wait and see.
Kojima just finished work on Metal Gear Solid HD Collection, has been teasing something new on Kojima Productions' new Fox Engine, and is also overseeing Zone of the Enders HD Collection. Metal Gear Solid: Rising will also be unveiled (again) at Spike TV's Video Game Awards awards next month, a game that he's working on but did not write or direct.
I’ve contacted Konami about today’s news, though I don’t expect to hear much (if anything) back.