After years on the shelf, The New Mutants has finally arrived in theaters, albeit in the midst of potentially the worst time to actually go to a movie theater. Either way, the film is actually here, allowing X-Men fans to see what Fox had planned for this group of young mutants back when its movie studio still existed. Since Disney purchased Fox, however, The New Mutants is the last film of that X-Men franchise, and it leaves plenty of questions about the franchise unanswered. See, as it turns out, The New Mutants is a bit more connected to the other films from the franchise, specifically X-Men: Apocalypse and Logan.
WARNING: This article contains spoilers for The New Mutants! Continue reading at your own risk...
Like X-Men: Apocalypse and Logan — two very different takes on the Marvel characters on opposite ends of the quality spectrum — The New Mutants ties directly to the classic villain Mister Sinister. At one point, when all of these films were being discussed, Fox was likely aiming to set up an over-arching story that eventually introduced Sinister as the big bad of the franchise, but that never came to fruition.
Throughout New Mutants, Dr. Reyes repeatedly mentions her "Superior," without actually revealing their identity. It's made clear that someone who isn't Reyes is watching over the whole facility. All of the teenagers think that she is working for Charles Xavier and the X-Men, and that they'll be sent to work with the X-Men once they get their powers under control. However, it's later revealed that Reyes is actually working for Essex Corp.
Sinister's real name is Nathanial Essex, and he founded the Essex Corp. to study and train mutants. Essex is teased in the post-credits scene of Apocalypse when a group of men show up to the Weapon-X facility to steal Wolverine's DNA. In Logan, the Essex Corp. is behind the creation of X-23. In New Mutants, Danielle Moonstar sees memories of a place where young mutants are being tested, and it looks almost exactly like the place where X-23 was created.
All of these movies were likely building toward the introduction of Sinister in the future, but that's not going to be happening now. The rights to the X-Men, and Sinister, are not in the hands of Kevin Feige and Marvel Studios.