Sony has seemingly revealed Uncharted 4 is coming to PC.
In a document published as part of Sony's Investor Relations day, Sony mentions Uncharted 4 under "more PC releases planned" (it's on page 26).
Sony is putting more of its PlayStation 4 games on PC. It's already released Guerrilla's Horizon: Zero Dawn on PC and, most recently, Sony Bend's Days Gone. It makes sense that Naughty Dog's five-year-old adventure game would be part of Sony's PC push.