I mean, sure, but that applies to any software purchase - the seller can change the license after it's been agreed upon. But in either case, why would you agree to such new restrictions? Just keep operating under the original license.
I do understand that for ye standard phone-home-for-permission rental situation, new terms like that could be unilaterally enforced by not supplying the "permission granted" response. And, worse, that circumventing such actions could put you in violation of DMCA junk. Which is one of the reasons I don't participate in standard phone-home-for-permission rental situations.
In the unusual case of the Jetbrains perpetual license, however - I don't see any mechanism by which they could effectively require me to re-activate a subscription in order to continue using the product. I have an offline and archived download of the version of software for which I have the license. I have an offline copy of the license file needed to continue using the product. I have firewalls that can prevent unauthorized network communication (such as phoning home). Short of sending armed thugs to my house, I don't see what their options would be for requiring me to do anything before continuing to use the product.
If I wanted to upgrade to a new version, it could absolutely become an issue - new version, new rules. But again, that's a potential issue with any software license, whether sane or subscription.
(Also, for perspective: one of the use cases for which they adjusted the payment model was "I do long-term work at a remote research station without internet access and need all my software to be operable without a network for indefinite amounts of time, so cannot use any software that requires permission even if it's only once a year. Hard to enforce changed terms and requirements on someone like that!)