I believe they said self-service could come back if either a.) the ship was 95/95 vaccinated; or b.) the self-service area is limited to only fully vaccinated customers and staff.
The first option would require most kids to be vaccinated, even the young ones who are not yet eligible for a vaccine. But there’s rumblings that we’ll see at least one of the vaccines open up for all kids in June.
The second option is not something I would think Disney wants to touch with a 10-foot pole - two classes of passengers, one of which has more liberties, and can do more stuff and go more places on the ship than the other? No way they’re going to go down that road if they can help it.