Rocket League is way overdue, we all know that, but honestly I am fully expecting it to arrive with the patch due in September named the 'Rumble Update'. This update will come with a bunch of stuff including a new game mode.
I'm speculating of course, so don't take this as solid confirmation of anything. The evidence is starting to come together though and I will be extremely surprised if Linux isn't released with the Rumble update next month.
Every time Rocket League is updated on SteamDB, the Linux depot is now also updated and this has been true for about two weeks now. This is the single most activity the Linux side of RL has ever seen being pushed into branches on Steam.
Originally the Linux version sat in its own "steamos" branch, but it seems like it has been finally put into their main testing branch named "psyonix". Why else would this happen if not to ready it for release? You can see the named branches on this SteamDB page.
On top of that, the Director of Development at Psyonix tagged me in a tweet about the Linux version recently too:
@darkgallium @RocketLeague @thenaughtysquid We're working on it, can't reveal the date yet
— Thomas Silloway (@Fuzzhead93) August 13, 2016
They are still being careful not to give any indicators after their previous failures to get it out.
I'm going to be honest, due to how long we have been waiting my patience for it started to wear thin. Considering how much activity it's seeing on SteamDB right now I am getting excited again! I just hope my own excitement for it doesn't get squashed again.
The game still has a crazy amount of people playing, right now there's around forty-four thousand people playing. So at least we aren't getting the game when it's dead, we are getting a still very popular game.