but after copyright expiration
I’m not at all convinced this is ever going to happen, and currently have no reason to believe it ever will.
While I agree copyright extensions are already to ludicrous levels and may get worse, never is a very long time. It’s just my opinion, but I think they’ll give up before they hit 10,000 years. Also, the fact that copyright terms are codified into so many multilateral trade agreements actually makes further extensions a lot more complicated than they were only a decade or so ago. Not impossible, but certainly more expensive.
Unfortunately, at that point no-one cares. The film is owned by the one company that’s notoriously one of the reasons of updating the whole copyright law and already none of their films have been made to public domain. With limitless money you can change the laws.