Does Adblock Plus plan to use the Embedded WebExtension before fully migrating to a WebExtension? That's the only way to automatically migrate user settings (e.g. filters).
I'm asking because the add-on version using an Embedded WebExtension would need to be released some time before the final WebExtension version so that all Adblock Plus users get migrated to this intermediate version before migrating to the WebExtension-only version.
Regards,
Michał