Psyonix has announced that a brand new Rocket League DLC will be released on March 5th for $4. Called the DC Super Heroes DLC Pack, the pack comes with the '89 Batmobile and The Dark Knight Rises Tumbler. A number of other DC-themed items will be part of the DLC as well including decals, banners, speed force boosts, wheels and more.
Items in the DLC are themed around several DC heroes including Aquaman, Cyborg, Wonder Woman, Flash, Green Lantern, Green Arrow and Superman.
You can learn more on the Rocket League site.