The image in question focuses on a new Metal Gear Solid 5 promotional poster. Next to the poster stands a cardboard plaque which contains words that are barely legible due to the size of the image in Kojima's original tweet. However, if you zoom in on the text, you're able to barely make out what the thing says:
Metal Gear Solid V Ground Zeroes
Prologue to Metal Gear Solid V The Phantom Pain
Takes place in 1975 after Peacewalker and nine years before the phantom pain
Multiple missions and central story and side-ops missions
Exclusive content for PlayStation platform
Videogamer came up with roughly the same interpretation of the blurry text as we just did, though we invite you all to take a crack at it for yourselves, either by visiting Kojima's tweet, or going directly to a much larger version of the image.
It is currently unknown what this PlayStation-exclusive content might be. We contacted Metal Gear publisher Konami for more information, but were met with a boilerplate "no comment."