Psyonix just announced their Fall roadmap details.
While RocketID and cross platform lobbies were supposed to arrive before the end of this year, things have changed. This has now been delayed until early 2019 but they are in talks with Sony to see if true full cross platform support can happen.
Rocket League will also get Xbox One X enhancements in the Early December 2018 update. They claim 4K 60fps but it remains to be seen whether this will be native or not. The December update will also bring a new Rocket Pass.
Rocket League is available on PS4, Xbox One, Switch, and PC platforms.