Basically, imagine that film director Bryan Singer is Michael Corleone and the X-Men films are the mob. Only he’s not upset so much as he is resigned and kind of happy about it.
Speaking to The Los Angeles Times, Singer talked about how Apocalypse is both the end of this particular trilogy and sets up the characters to be who we met in the original 2000 movie. (That sets up a complicated canon tangle that is best not to think about.) But Singer also addressed whether or not he’d be sticking around for more films, saying:
I recently met Danny Boyle — he and I have known of each other for many years but never met. He was prepping “Steve Jobs” at the time and I was doing this and he said, “Are you going to be doing ‘X-Men’ movies forever?” And I didn’t actually say no.
The reality is, even though I’m very desperate to jump to something completely different, I’ve spent so many years in this universe and I love this cast and the characters so much, I just don’t see myself abandoning them forever. Perhaps as a consultant, as a producer, even as a director, I could see myself returning in the future. Just right now, once this one is done, I’d like to do something really different.
In this particular universe, we’ve already got the third standalone Wolverine film, X-Force, Deadpool 2, the troubled Gambit, and New Mutants all supposedly in production. They’re all spinoffs to the core film series that can take up years before Singer returns. Or they can slot an X-Men film with a different director in between two of those. We already know from Simon Kinberg that they next one will be in the ‘90s.
Eventually, Singer will return in some capacity. Just when he thinks he’s out, probably.