The Rocket League cross-platform party system will be released in February, development studio Psyonix announced earlier this month. The update was reportedly delayed because Sony's PlayStation 4 console did not support the system.
The cross-platform multiplayer update was already announced in August. The studio called the system Rocket ID but has since moved towards the more generic term Friends List.
Cross-platform parties via the new Friends List system was delayed in October. A specific reason for pushing the update to 2019 wasn't given, but it was likely related to getting permission from Sony to support cross-platform multiplayer on its PlayStation 4 console.