Rocket League started off as a fun little soccer/racecar hybrid that nobody expected to be a worldwide hit. There's no way Psyonix expected it to be as big as it is today. Meeting such a large demand is something an indie developer may not have the means to achieve.
Originally, Rocket League's publishing was assisted by 505 Games, but now the publishing rights have been handed over to Warner Bros' gaming branch.With the handover, a newly updated physical version is on the way.
It has yet to be seen what will be included in this in this new version, but it's likely safe to assume it will be substantial enough to warrant a new package. In a press release, both Warner Bros. and Psyonix made positive statements on the new joint venture.
Kevin Kobodeaux, Senior Vice President of Sales, Americas at Warner Bros. Interactive Entertainment said:
"Rocket League has such wide appeal across all audiences, it’s no wonder the game is such a huge success. We’re very excited to be working with Psyonix to bring the game to retailers across the globe."
Similarly enthusiastic, Vice President of Publishing at Psyonix, Jeremy Dunham stated:
"Warner Bros. has already proven to be a great partner. We first collaborated on Batman v Superman DLC for Rocket League in early 2016 and we have continued to be impressed with the team’s knowledge, professionalism, reach and enthusiasm for video games. They are the ideal partner to help us push Rocket League to another level at retail."
Again, there is very little work on this new version of Rocket League, but given the upcoming Nintendo Switch release this holiday, that's likely a good place to start looking.