Everybody's Gone to the Rapture was included in a list of leaked Steam games a while back, but there's new evidence that it will indeed be coming to PC.
Banner art was added to the game's Steam database entry yesterday. This indicates that an announcement could be on the way very soon.
There's also the editing of packages, including 'Everybody's Gone to the Rapture for Beta Testing', and 'Everybody's Gone to the Rapture Developer Comp'.
It could still be a hoax, but it's a thorough one if one. Now we just have to wait for The Chinese Room to make an official announcement.