So what? I hear you say, Xbox & PC have had cross platform titles before so it's only natural that more titles will introduce this feature in future as more developers get to grips with the tech. However it seems Microsoft & Rocket League developer Psyonix have said that this cross platform play could be extended and allow Xbox players to not only play with PC players but PlayStation players too.
Rocket League Xbox & Playstation Cross Platform Play?
Rocket League Xbox & Playstation Cross Platform Play?