"Konami recently showcased a 30 minute long gameplay demo of the upcoming Metal Gear Solid V: The Phantom Pain at this week's E3. A number of select media were invited and GamingBolt was fortunate enough to be a part of behind the closed doors demonstration of the game."
Update 2: A post on the official PlayStation blog claims that it is indeed 1080p/60fps. Also tweeted by Kojima's personal assistant and re-tweeted by the man himself. This about confirms it.
Update: A Konami representative got back to us and he stated that he was unaware of any mention of the resolution or frame rate of the game in any of the demo sessions.