Psyonix has confirmed that it will be releasing an update so Rocket League will support PS4 Pro features, with this going live on February 21st. This update means the game will run at 1080p at 60fps on the standard PS4 while this is upped to 4K at 60fps on the Pro. This will be seen in all arenas in single player and two player split screen, while for three and four player split screen only some of the arenas will boast the same attributes.
At the same time the Hot Wheels DLC, which was announced last week, will be available to purchase on the same day.
Source: PS Blog