Rocket League developer Psyonix has been in bed with WWE for a while now, with several special wrestling events being sponsored primarily by Rocket League. Now, the logical extension of the partnership is happening, and WWE stuff is coming to the video game side. Also, WrestleMania is coming up, and Rocket League will have a presence there as well.
This partnership will continue through 2018, with several sponsorships for live WWE events, such as most recently sponsorship for last night’s Elimination Chamber. Rocket League will also be making appearances on WWE Superstar Xavier Woods’ UpUpDownDown YouTube gaming channel. The weekend of April 8, 2018 is WrestleMania 34, and Psyonix will be there with playable Rocket Leagues setups for attendees.
Finally, Psyonix also announced that in-game customization items featuring WWE iconography will be coming to Rocket League, starting sometime in April. Psyonix has not provided any details for these new items, but I would expect to hear more closer to the WrestleMania media blitz.
Source: Rocket League official site