For existing CTA4 plugin users, you can freely upgrade your CTA4 plugins to be compatible with CTA5.
Here's the redeem link:
https://www.reallusion.com/campaign/default.html?cid=301&chk=fd84d4553a7ddf239e66d455c4e3e92c
Please note that if you purchased a CTA4 bundle with a plugin after Sep 1st, 2022, then you've got the plugins serial numbers for CTA5 and the plugins serial numbers for CTA5 in the same order. Kindly check in the product registration page:
https://www.reallusion.com/member/#/en/registration