Ava Duvernay has declined to direct Marvel’s Black Panther project, from Entertainment Weekly link below. I am not surprised that Duvernay turned down the project because at this point Marvel is so entrenched in their universe. When a director takes on a Marvel movie, they have to make the film that Marvel wants them to make. That is why Edgar Wright left Ant-Man, that project was in development before Marvel had the universe but when Marvel had their universe Wright was no longer making the Ant-Man film that he wanted. This is the reason I think Marvel needs to leave their universe and do projects that exist outside of it because one thing that Marvel has been doing well is attaching grade A talent to their projects. If they keep having, these directors follow strict guidelines in making the films then they will stop having this flow of top-level talent because the film would not be theirs. That would leave Marvel with B or even C level talent.