There’s no contract stipulation, and there never was. It was always just a guess.
Seems like an educated guess at this point, though I’d love to be wrong.
I don’t believe anyone at Disney would sign a contract that said “you see that money on the table? You can’t use it. You have to sit on it.”
Them wanting to “respect” Lucas’ wishes, I can get, but swearing they won’t ever release it seems vindictive, even for George “MacLunkey” Lucas.