Question about buying into perpetual and updates

[SixChurchStreet]

I'm currently on a subscription, about to expire. I'm happily running 2020.12 and don't really have a need to go beyond that when v2021 starts rolling around. I'm on a Mac Pro 5,1 running High Sierra, and I'm happy to stay put.

But I may be buying into a perpetual just so I don't need to subscribe anymore.

Say I buy Perpetual with the year of updates, and I don't update during the next year. I stay on 2020.12. Then say a year and a half from now I get a new computer and I'd like to move up to 2021.x. Will I have access to the newer versions that were released during the period that I was covered by updates, or is it a case of being stuck wherever you are if you don't update (in my case still at 2020.12)?