We've made one change since we last discussed it: Specifically, Ilija realized that __set's behavior is already inconsistent, so supporting it for aviz properties with invisible set would make it even more inconsistent, not less. For that reason, we've changed the __set behavior such that a non-readonly aviz property will not trigger __set. Further details are in the RFC, but in short, all of the use cases for that behavior now have better alternatives, such as property types, hooks, and aviz itself. So there's really no point to falling back to __set in edge cases.
https://wiki.php.net/rfc/asymmetric-visibility-v2#interaction_with_set_and_unset
Baring any new developments, we plan to start the vote early next week.