Microsoft has announced that it is working to make XBox and Win 10 games compatible with other consoles and platforms. It is beginning this experiment with Rocket League that will begin with XB1 and PC players facing off against one another and "an open invitation for other networks to join later".
First, in addition to natively supporting cross-platform play between Xbox One and Windows 10 games that use Xbox Live, we’re enabling developers to support cross-network play as well. This means players on Xbox One and Windows 10 using Xbox Live will be able to play with players on different online multiplayer networks – including other console and PC networks.
Of course, it’s up to game developers to support this feature, and Xbox Live players will always have the option of choosing to play only with other Xbox Live players. We’re thrilled to confirm that Psyonix’s Rocket League will be one of the first games to take advantage of this new capability by enabling cross-network play between Xbox One and PC players, with an open invitation for other networks to participate as well.
Read more on the Rocket League site.