In a post on their Windows Blog, Microsoft revealed that Gears of War 4’s cross-play support between PCs and Xbox One is now official. Prior to this, the feature was in testing but it looks like it will now be available for all gamers, but take note that this is only for the Social Quickplay feature.
According to Microsoft, “Core and Competitive will remain platform independent, only matching Xbox players with each other and Windows 10 players with each other. Despite the closely matched performance between users on both platforms seen in our cross-play Test Weekend, we always want to ensure our Ranked experiences are as closely matched and competitive as possible.”
Basically it seems that if you want to get in a quick game or two that isn’t ranked or “serious”, then this will be something to look forward to. However if you’re more of a competitive gamer then we guess you’re out of luck as far as cross-play is concerned.