I'd imagine the only way that would be possible is if the company wasn't sold, just it assets.
If, for example, Lucasfilm owed a billion dollars to authors then sold the rights, past, present, and future, of everything Star Wars to Disney and then went out of business - then, yeah, Disney gets Star Wars and isn't beholden to any pre-existing deals because they bought some IP and not the company. However, not sure how you can sell the entire company and exclude the obligations. The obligations are under Lucasfilm. Now, sure, you could create a sale where since George was a sole owner, that responsibility is retained by him. However, that would be things like debt incurred in buying the Presidio or something like that. The logic people are trying to use here would be right up there with saying Lucasfilm would now no longer be required to pay royalties to Mark Hamill, Carrie Fisher (estate), and Harrison Ford, among others for the OT because the company changed hands.
The only other way you get out of debts and obligations would be if the deals signed by those parties said they relinquish rights to those payments if Lucasfilm is sold. If there's nothing in the deals signed by the third party, you can't exclude them when selling the company.
The differences you see out there are Time Warner sells HBO to Amazon. Now, i know that didn't happen, but still..In that case HBO can be sold to Amazon and Time Warner can retain debt - they can't keep royalties because those are tied to what was sold. But you do see deals where things like this happen and it says Time Warner will keep 2B in debt and things like that.