If you can't make a profit off of a licensed property after 35 years of exclusive control, you've done something horribly wrong. If you sit on a licensed property and do nothing with it for decades, it should be allowed to revert to someone else, or better yet go into public domain.
Of course, what they should do is have the copyright expire after 35 years. Then if the original creators want to make sequel at that point they're entitled to -- just like everybody else.
This happens ALL THE TIME. 2001 A Space Odyssey, Heavy Metal (1981-Blue Oyster Cult), Rocky (1976) airing on TV without Eye of the Tiger, It's a Wonderful Life was public domain but distributors needed to pay for the soundtrack. TV shows like Married with Children and Dave airing in syndication with different opening theme songs. etc.
All over archive.org you'll find tons of classic films but with the soundtracks stripped out.