Developer Psyonix has announced that it has pushed its plans for expanded Rocket League cross-platform functionality into early next year. However, one silver lining is that Sony's recent announcement of cross-play support--led by demand for Fortnite among others--means that the studio can prep its plans to work across all platforms, including PS4.
The announcement came as part of the Rocket League roadmap. The backbone of the feature will be RocketID, it's connected account system that will allow features like friends lists and parties across all platforms. That system is apparently taking longer than the studio expected.
"While our goal was to release RocketID before the end of 2018, we've made the difficult decision to push its release into early 2019," the announcement said. "The good news is that with Sony's recent announcements regarding full cross-platform functionality, we can now make additional changes to prepare RocketID for ALL platforms should we receive permission to do so! We're working incredibly hard to ensure that it’s as intuitive, stable, and polished as possible, before releasing it to the world."
That mention of permission is also key. Sony has let Fortnite begin to work cross-platform as a beta test, but it has been unclear about when and which games will be prioritized next for the functionality. Rocket League is one commonly requested game and actually had been generating demand for cross-platform play before Fortnite drove demand up even further. Psyonix had expressed frustration with Sony for refusing to budge on cross-platform play, despite having figured it out early.