I gave in and bought all the existing steal books when I learned Fox permenantly owns the rights to A New Hope.
Fox owns the distribution to Star Wars (77) permanently. They don't own the content of the film. Lucasfilm can change the content however they like. They just can't distribute whatever they do to it (further change, leave alone, revert completely, any stop inbetween there) without striking a deal with 20th Century Fox first. And 20th Century Fox can't distribute the film unless Disney and Lucasfilm agree to let it be distributed.
Now, the fact there's already been another blu-ray release from Fox, and a digital release from Disney, means they're absolutely up for mutually benefitting each other. So the original versions not seeing release has nothing to do with the distribution rights. It's 100 percent Disney/Lucasfilm's call.
So far as we know, those 4K remasters aren't the originals.
Doesn't mean they can't alter them (essentially make their own Despecialized Editions) at some point along the way.