SPOILER WARNING: The following article contains absolutely massive spoilers for the end of M. Night Shyamalan's Split. If you have not yet seen the film, and don't wish to know any details about the movie, please bookmark this link and return to this feature after your screening!
Many filmmakers have learned hard lessons about sequel rights in the history of Hollywood. Unless specific deals are made, studios have the power to capitalize on titles any way they see fit, and sometimes this happens at the horror of the original creators. This is something that will never happen to writer/director M. Night Shyamalan, however. This is because he retains certain sequel options to all of his movies -- which is what allowed him to make Split as Unbreakable 2 despite being released by different companies.
After seeing Split at its Los Angeles premiere at AFI Fest last fall, one aspect of the film that surprised me was the movie being distributed by Universal Pictures -- given that Unbreakable was released by Disney's Buena Vista back in 2000. When I had the opportunity to sit down one-on-one with M. Night Shyamalan the next day, I asked him how it happened, and explained that it's in his contract to retain certain sequel rights for his films. Said Shyamalan,
Luckily I took care of all the right stuff. I had it all arranged, and everyone was fantastic about it, and everything like that. So it worked out great on that front. I kind of own the sequel rights to all my movies; not own, but nobody can make a sequel to my movies without permission. I gave up whatever I needed to give up to make sure I had those over time, because I figured 20 something years from now, I'm going to be pretty upset if [someone made a sequel without my involvement].
Split is the first sequel he's had the opportunity to make, and it certainly doesn't look like it will be his last either. Because of the Unbreakable tease featured at the end of the movie, there is every reason to believe that we will eventually get to see Bruce Willis' David Dunn face off with James McAvoy's Kevin Wendell Crumb. As discussed in another article from my interview with M. Night Shyamalan, it's something that the writer/director definitely wants to do, but right now it's merely a concept rather than a fully-fleshed out idea.