The next season of ranked Rocket League begins next week, on Tuesday, August 27. A day later on Wednesday, the 28th, Rocket Pass 4 will kick off with new items to unlock in the usual free and paid versions.
Mudcat is the new car, which is unlocked when you buy the premium Rocket Pass. It's inspired by rally cars, and there's a G1 version at tier 25, and a GXT version at tier 70, as seen in the trailer above. Personally, I wish it looked more like a Peugeot 205 or something. It doesn't even look much like the typical modern rally cars, now that I think of it, unless Ford Fiestas are significantly different than I remember. But I'm nitpicking.
You'll have quite a long time to unlock tiers, as this Rocket Pass doesn't end until December 4. As usual, the premium version costs 10 keys, which comes to $10. Or you can spend 20 keys to skip straight to tier 12, but no one I know has needed to do such a thing—I'm at tier 257 in the current Rocket Pass. Maybe I just play Rocket League too much.
The start of season 12 also means that this is my last chance to crack Champion rank in Snow Day (the good mode that you should play) and earn that season reward. Best of luck with your own ranked journey, and next week's reranking, if you're also a person who cares about Rocket League ranks enough to think about them when not playing Rocket League.