Well, for what it's worth they are all guardians of their own planets. If you subscribe to the world-building assumptions from fans based on Codename: Sailor V SilMill flashback scenes, then the Inner Senshi will still have their roles in ruling over their own courts and civilizations on their respective planets. Either way, they still have an everlasting mission to protect and support Usagi. I guess their fate depends on whether she actually dies or lives on forever in some other way... So no, I don't think they'd be redundant because they're not tied to the current ruler of Crystal Tokyo as far as we know.