People love the classic ships. I don’t ever see them scrapping them. I feel like they may possibly become more “niche market” or “specialty cruise” vessels as the other new ships come online, but as long as they can keep them I good enough shape, they’re going to be money makers (post-Covid).
and then, when they’re finally too expensive to continue to keep them seaworthy, they’ll park them somewhere and make them a Resort Hotel, just like the Queen Mary (which Disney did own at one point!).
People that can’t afford a full cruise (either the time or the money) could have an “immersive cruise ship experience”, staying in cabin for a night or two, or just making a (paid) dining reservation for Rapunzel’s, Tiana’s, or Palo, or buffets at Cabana’s/Lumiere’s/Tritons.
They could even have a few decks that they sold off as DVC studio cabins. I could say my home resort is the Wonder, lol.