Not
quite true AFAICT. You'll have to register as an android developer and use your own signing keys, or use some sketchilly acquired/disseminated signing keys. The apps don't have to be actually published/acquired through the app store, but their authorship signature has to be able to be tracked back to _someone_ in Google's big DB. Someone may even just decide to include their keys into Revanced manager to allow it to keep working; we don't know what Google will do if someone just brazenly says "sure, I'm a registered android developer, and yeah, my signing keys are used to sign tons of apps that all seem to be named 'Revanced' on many people's phones. What of it?" Maybe Google will try to ban them, maybe they won't. They've not released any explanation of what they'll actually do once all apps have to be signed.
Please correct me if I'm wrong, that was how I understood the recent announcements.