Update: as per an announcement at Gamescom earlier this year, Killer Instinct Season 3 actually has a confirmed release window of March 2016 for PC.
Back in June we learnt that Gears of War: Ultimate Edition is coming to PC. Then, when it released for Xbox One but didn't for PC, several months passed before we were assured that it was "still coming to PC". That's about as vague an assurance as you can get, but now Microsoft games honcho Phil Spencer has indicated on Twitter that the release date "won't be too far into 2016".
That's pretty vague too, but it definitely rules out that Gears of War: Ultimate Edition will release in 2017, or 2020. Responding to a fan query, Phil Spencer indicated that the same applies to Killer Instinct, the free-to-play fighter reboot that has been on Xbox One since the console's launch in 2013.
Still, if you hunger for a revamped Gears of War experience on PC, the remake will come with features that'll put it ahead of the console release, such 4K resolution, DirectX 12 support and an uncapped framerate.