I doubt any such thing was signed anyway
Hard to say, but regardless of that, I think the studios in general give quite a lot of deference to a film’s director (on the issue of home video releases, that is). Star Wars is hardly the only film where some shitty director’s cut is given priority over the theatrical cut. And while Lucas only directed one of the films, I think Disney will still defer to him on the whole trilogy out of some sort of misguided sense of professional respect, even if they’re not legally obligated to. I expect that will continue even after death (see the Narnia reordering fiasco, where publishers interpreted a letter where CS Lewis humors an enthusiastic fan as justification for still effing up the whole series 50 years after the man is no longer capable of being offended by their publishing choices).
There likely will not be an official release of the Star Wars trilogy on home video until the copyrights expire and we get a good public domain release.
And this is why we have fan preservations.