Isn't WordPress already compatible with PHP 8? Omar advises caution:
“[My team] is highly doubtful. It’s really not possible to tell. […] [T]he sheer amount of breaking changes and the type of changes included in PHP 8, plus some added complexities in cross-version tooling, make this compatibility challenge a different beast from what we’ve seen before.”
It sounds like Yoast is making progress preparing for PHP 8, and they (along with the whole community) will be keenly interested in reactions to this report.