We don’t have any plans to continue to support CentOS 7 or RHEL 7 now that it has reached EOL. We have always said that we support OSes throughout their general availability, and once they reach EOL, we stop testing/development there (we don’t break it, intentionally, of course, and you probably have a couple years before Virtualmin starts actually breaking on RHEL 7).
If enough users of RHEL7 (not CentOS 7, as that has no extended support from Red Hat…you have to switch to RHEL if you want to keep running it with security updates) wanted to pay for extending support for the old way of doing things, I could be convinced (but it won’t be as cheap as the usual Pro license). Find me a dozen people willing to spend, say, $10/month for extended support, and I’d be willing to keep building out Apache with custom suexec…but I really want to stop doing that, and I think y’all should want to stop using it, too. PHP-FPM is better for almost every use case.