Yes - your old Opt-Out Link will remain functioning. Once Opt-Out Links are deployed using the new domains, we will keep the existing Opt-Out Links active.
*Please note - as noted above we will never disable old Opt-Out Links. However, if you delete an Opt-Out List, delete the domain, or change the CNAME from the system default domain, the old Opt-Out Links will remain functional.
To learn more about the benefits of adding Opt-Out Domains in SUPPRESS, please review this article: How to Add a Domain to my SUPPRESS Account
If you have further questions, please contact us: firstname.lastname@example.org