Alright, we have to move on after the tragic death of Robin Williams as he will always live on through our hearts, minds as well as the many movies he's done over the years.
Konami recently held a livestream on Twitch where they revealed that MGS5: The Phantom Pain and its very small prologue Ground Zeroes is coming to Steam and it couldn't be any better news as we haven't had a PC port of any Metal Gear Solid game since MGS2, Metal Gear Rising is just a spin off of the series so it doesn't really count.
Kojima himself has said that Ground Zeroes will naturally be released before The Phantom Pain as it sets the stage for the events that Big Boss is gonna face in MGS5.
And the reveal itself couldn't have been more glorious, in a gameplay video that Konami showed during the livestream, Big Boss puts on a box that has a valve in the back and on the sides are the logo of the Valve's Steam service, it even lets Big Boss blow steam from underneath the box AND make the noise that a steam train's whistle would make.
Here's an article on the english PC Gamer website about the reveal as well as the recording of the livestream itself:
Also if you search for Metal Gear Solid on Steam, you will be able to find their store pages, however as of yet you can't preorder either Ground Zeroes or The Phantom Pain.