Update: Series creator Hideo Kojima has officially confirmed Steam versions of Metal Gear Solid V: Phantom Pain and Ground Zeroes, following an earlier leak. He held off confirming a release date.
Original report continues:
The revelation comes from an assumedly premature post via the official Konami UK website, where the headline and link to the announcement appeared briefly, just ahead of Konami's MGS V live event.
Both games have only previously been confirmed for release on PS4, PS3, Xbox One and Xbox 360.
Konami's special Metal Gear Solid 5: The Phantom Pain event is set to get underway shortly and you can watch the whole thing live here.
Kojima will present new gameplay of the game to showcase the "impressive capabilities of Kojima Productions' breathtaking FOX Engine and more".
In addition to the new gameplay presentation there will also be Q&A session and "a few surprises", presumably one of which will be a Steam announcement.