Update 18/5/2018: Five years later, the video has been released on Youtube.
Hideo Kojima, along with a few other staff members from his studio, is holding a presentation at the Game Developers Conference 2013.
The main focus of the presentation will be Fox Engine, the newly developed game engine by Kojima Productions. There will also be a new trailer for Metal Gear Solid Ground Zeroes, and Kojima will make an announcement of some sort as well.
The presentation, called Photorealism through the eyes of a FOX: The Core of Metal Gear Solid Ground Zeroes, will take place today, on 11:00 AM PST. It will take between 75 and 90 minutes.