In case you weren’t aware, works created and published between 1978 and 1989 as works-for-hire have a copyright term of 95 years from publication. And since Heathers had wide U.S. theatrical release in 1989, it falls within that window.
So, 59 years from now, Heathers will enter the public domain. What this means is that anyone will be able to use, adapt, and build upon the original film without seeking permission, paying licensing fees, or risking copyright infringement.
Once in the public domain, you can adapt the story, characters, and dialogue into new creative formats, such as making sequels, prequels, remakes, or new adaptations for different mediums. Additionally, you can alter settings, time periods, or character dynamics, and could legally sell, monetize, and profit from these works without paying a single cent in royalties.
The only thing is that this only applies to the original 1989 film, the musical, the 2018 TV show, and individual copyrighted songs on the soundtrack all have their own separate expiration dates. Plus, trademark laws on the name itself might still apply.
So, uh, just 59 more years until we can legally do whatever we want with the story.