Phase III of Marvel Cinematic Universe doesn't begin until 2016, but already most of its film releases have directors, well ahead of production getting started (save for Captain America: Civil War, which is already filming). Marvel Studios president of production Kevin Feige has indicated that Thor: Ragnarok may be the next Phase III to officially secure a helmsman, though we know the studio has already begun approaching candidates to direct Black Panther too.
Black Panther, which will be the first solo movie headlined by Chadwick Boseman (42, Get on Up) as T'Challa after his onscreen debut in Civil War, was at least one project that Marvel approached Selma director Ava DuVernay about taking on. The acclaimed filmmaker recently teased the possibility of her calling the shots on Black Panther (by way of Twitter), but has since revealed that's not going to happen after all.
DuVernay has confirmed to Essence that she's passed on directing Black Panther, as she joked that she will "declare my independence from this rumor" in honor of the impending 4th of July holiday. Here's the explanation she offered, for why she's decided against taking on the task:
“I'm not signing on to direct Black Panther. I think I’ll just say we had different ideas about what the story would be. Marvel has a certain way of doing things and I think they’re fantastic and a lot of people love what they do. I loved that they reached out to me.”
The director added that she "loved meeting Chadwick" and the various Marvel personnel, but that ultimately she and the studio had different creative visions for the film. As DuVernay put it, "Better for me to realize that now than cite creative differences later."
DuVernay certainly isn't the first director to part ways with Marvel on a project well before production begins; Patty Jenkins did the same on Thor: The Dark World, well before she moved on direct Wonder Woman for Warner Bros./DC instead. Comparatively, Edgar Wright spent several years developing Ant-Man before he pulled out as director shortly before shooting was supposed to start (allegedly due to Marvel having made script changes without his consent). Marvel Studios has quite the impressive track record at the box office (and, for the most part, critically), but as illustrated by these examples, they're not always accommodating to filmmakers with distinct voices and styles.
However, while there are now a number of directors who've publicly admitted to having struggled while they worked within the Marvel Studios system (Joss Whedon and Alan Taylor among them), there are storytellers like James Gunn and Anthony and Joe Russo who thus far seem comfortable working under the Marvel umbrella. As for DuVernay, she had nothing bad to say about her experience (brief it might have been) with Marvel, and remains firm in her support of the Black Panther movie happening:
"I love the character of Black Panther, the nation of Wakanda and all that that could be visually. I wish them well and will be first in line to see it."
Ant-Man opens in theaters July 17, 2015; Captain America: Civil War – May 6, 2016; Doctor Strange– November 4, 2016; Guardians of the Galaxy Vol. 2 – May 5, 2017; Spider-Man reboot – July 28, 2017; Thor: Ragnarok – November 3, 2017; The Avengers: Infinity War Part 1 – May 4, 2018; Black Panther – July 6, 2018; Captain Marvel – November 2, 2018; The Avengers: Infinity War Part 2 – May 3, 2019; Inhumans – July 12, 2019.