I suppose if something can be commercialized, humans would do it, happily and forever. It doesn't matter how culturally significant it is (like the MLK speech). Money first, I suppose
All this to say, don't expect anything to enter public domain anytime soon.
https://observer.com/2023/02/so-mickey-mouse-is-about-to-ent...
Things that entered the public domain this year: https://publicdomainreview.org/blog/2023/01/public-domain-da...
“They don’t have my permission to use my music!”
They didn’t need it, you’re getting paid, shut up and be the whore like the contract you signed says you are.
Setting aside your concerns about how poor, helpless politicians are being bullied by all-powerful artists, the fact is that licenses often have carve-outs for conventions and other campaign events. Artists can also prevent use by arguing that it infringes on their Right of Publicity or the Lanham Act.
Anyway the point I am badly making is that I am pretty sure the educational value of his speech on say wikipedia outweighs the benefit of dragging some idiot remixing it to say rude things through the courts.
Not sure if the librarian who taught the class still uses that site, but as a 13 year old it was a very powerful lesson.