I’ve been hearing conflicting information about this. That it’s going to be a new game or that it’s just a tech demo for Kojima’s new Fox Engine. Some sources are saying that it’s just Metal Gear and others are having the Solid in there as well. It’s supposedly going to be still a prequel that takes place after 3. Open world seems to be part of it also. The link above is a description of some gameplay from it. There’s also supposed to be 30 minutes of gameplay uploaded at some point today.
While I kind of wish they would just let Metal Gear (Solid) die as 4 I felt was a nice conclusion, I’m pretty excited.
Edit: A pic from the coming gameplay video.
Kojima has said that this is running on a PC “similarly equipped to a PS3” and will be running on current gen systems. Either he’s full of shit or he’s a wizard.