Recently, it was confirmed by FamedChris on Twitter that, for the first few weeks of Chapter 2's release, Mad City will remain in Season 7 "to give players an extra chance to get all of the rewards with the new balancing".
If I remember correctly, the developers (or a developer) held some polls about how users felt about the flow of leveling up. I'm having some trouble finding these, but I do have the follow-up Tweet from FamedChris.
I'm not sure what the exact nature of this change will be. I'm assuming it'll have to do with the skins beyond level 100 although it could potentially address the lower levels as well.
The takeaway, here, is that if you haven't gotten all of the rewards yet - don't sweat it. They're going out of their way to give players a chance to unlock them once Chapter 2 releases. If anything, it's worth waiting to save yourself the trouble.