When mozilla allows between session updates of static filter list, the biggest hurdle is solved for adblockers. This should not be to hard to implement as a seperated (update_filters) API.
I can imagine that Gorhill will re-releases uMatrix again, only without host based filterlists (like NoScript is now). uMatrix with its own rules only would function like a NetRequest firewall where you can block all (paranoid mode), third-party (hard mode) or third-party scripts and frames (medium mode) and selectively allow (user picked) net requests to whitelisted domains.
The community maintained whitelists (recipes) probably would be the only assets used by this revived uMatrix net request firewall. By updating uMA every month the recipes would be updated monthly also.