Miller never officially signed on for Deadpool 2, though he was developing the script and gave every indication that he planned to return for the sequel.
The Deadline report explains that the creative differences were mutual and that Miller exited the project amicably. 20th Century Fox, for its part, still thinks highly of Miller and plan to attach him to the film adaptation of Daniel Suaraz's novel Influx, which has the potential to become a film trilogy. Mark Bomback is writing the script for Influx.
Clashes between a director and his star aren't unusual in Hollywood, though normally it is the actor who ends up leaving a project. That really wasn't an option for Fox with Deadpool, as Reynolds' pitch-perfect take on the character is a much more distinctive draw for the franchise than Miller's directorial capabilities, not to mention that Reynolds is a producer on the film, alongside Fox's own Simon Kinberg and Lauren Shuler Donner. Knowing that there was no way forward, Miller reportedly removed himself from involvement with the film.
For fans, Miller leaving Deadpool 2 will feel a bit like breaking up the band. Miller, Reynolds, and writers Rhett Reese and Paul Wernick had been trying to get Deadpool made for more than five years, but the poor reception for Reynolds' debut as a version of Deadpool in X-Men Origins: Wolverine made it a hard sell to fox. The huge fan reaction to leaked CGI Deadpool test footage in 2014 put development back on track. It seemed that this group underdogs had finally gotten their way, and the box office take certainly backed that up.
With Miller now gone, fans are sure to start wondering if that perfect alchemical mix of talent is gone for good.
Which leads to the natural question of who should replace Miller. Deadpool was produced on a relatively small budget, but the huge box office return makes it a much higher profile franchise now. Will Fox go for another relative unknown for Deadpool 2, or will they give their new darling franchise to someone with a proven track record?
Deadpool 2 will see the Merc with a Mouth return for another hilarious misadventure. The sequel is said to introduce Cable, the time-travelling mutant X-Men and X-Force character who frequently partners with and plays straight man to Deadpool.
The film is also said to introduce the mutant mercenary, and Cable's love interest, Domino. Reports suggest Fox is narrowing their casting search for Domino, and the short list of actresses include MacKenzie Davis, Lizzy Caplan, and Mary Elizabeth Winstead.