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.
On January 14, 2019, the studio announced that the PlayStation 4 version of the game now also supports cross-platform multiplayer matchmaking. However, players still can't make parties with players from other platforms.
The Rocket League cross-platform party Friends List system will release in early February. It will support PC, Xbox One, PlayStation 4 and Nintendo Switch.