Crackdown 3 will be coming to the PC as a "Play Anywhere" game. That means you can buy it on one platform and access it from either the Xbox One or PC. That is the good news. The bad news is that it won't be out until 2017 and when that happens it will be sold only to Windows 10 users (Windows 10 Store) in addition to the Xbox One release.

Dave Jones from Reagent Games made some remarks about the ongoing development hell that Crackdown 3 seems to be stuck in.
Crackdown 3 is a game built for the future with a multiplayer experience that will redefine what it feels like to play games, and as we continue to work on this, it has become clear that our original timeline of delivering multiplayer to fans this summer, while maintaining the size, scope and quality of the game, would be challenging. Our top priority is to give gamers an experience they have never seen before at a scale never thought possible, and sticking to our original timeline would have compromised that goal.

We know that many are looking forward to becoming Agents in Crackdown 3 and we are committed to delivering the best experience in 2017. This decision was made with our fans and their gaming experience in mind.