Pretty much what happened to authors of novels.
I know authors usually use publishers for review / editing / publication, but I'm not aware of a time where the relationship was not "publisher gets X% cut of revenue". When was it "author gets X million dollars"?
The same applies to music. Pretty much every creative industry outside film is paying the performers or creators a percentage of sales. Its just harder for that to scale to endeavors that take thousands of people like modern blockbusters.
For performers, actors in plays, members of an orchestra, backup dancers behind a pop star... most are getting paid per performance or per period of time, not royalties. Royalties are more common for people who can take a majority responsibility for the end product, e.g. a solo artist or an author.
(Royalties aren't rare either, but a lump sum agreement isn't eyebrow raising in the least)
I think some of the low to medium budget movies will make the transition to simultaneous streaming releases where it may be easier to recoup money early on. This may or may not force a similar thing to happen with big budget films, but too many lifestyles would be affected for this to happen in any short to medium term.