Rocket League's next season will begin on Tuesday, 27 August 2019. It will bring Rocket Pass 4 in tow along with a pile of rewards that the mechanic will offer, such as new vehicles and goal explosions that are somewhat smokey apparently.
Rocket Pass 4 will not differ from the previous ones in the core workings of the feature. There will be a free and a paid track, each with their own rewards but having the paid pass also gives access to the free rewards, which is kind of obvious.
The new car that will be featured in the next pass is the Mudcat. According to the trailer above, the regular version will be unlocked at Tier 1, the G1 version at Tier 25 and GXT version at Tier 70. As you can imagine, there are more details and livery on each subsequent version, culminating in a really fancy looking car at Tier 70. It's the red one on the left of the header image.
Just like Season 12, the new Rocket Pass will kick off on 27 August 2019 and there will be a decent period to grab as many rewards as you can from the grindfest since the reward unlocking will conclude on 4 December 2019. Pricing will be the same as before, standing at 10 keys which translates to $10 / €8.70 /£7.99.
Skipping tiers will be available just like before but spending money on a pass just to spend more money to progress it sounds a bit odd. Over two months should really prove to be enough time to grind out that sweet Mudcat GXT as well as the goal explosions. Speaking of which, you can see one in the trailer at 0:33 and another one at 0:37 but it didn't specify which Tiers will unlock the goal animations.
Since Season 11 is coming to an end, this may be a good time to try for that last push to get the desired rank, provided you are close enough to get to it in five days.