On Monday (14), Psyonix announced that the Rocket League game will gain cross-play on all platforms, including the PlayStation 4.
From this date, the game will have on the same servers the online players of PlayStation 4, Nintendo Switch, Xbox One and PC, through Steam. The feature is already active on all consoles.
This was the second game to receive cross-play on the PlayStation 4. In September 2018, the game Fortnite was the first to receive this feature on PS4, after much internal resistance and pressure from players, companies and even competing executives (Phil Spencer, on Twitter).
Sony has a long history of resistance to cross-play, so the function is still extremely limited.