Like Jazzy B said, I think Marvel's wary of touching BP for fear of mishandling it. I mean, do you keep the name, which is connected at the hip to the activist group? Do you change the appearance of Wakandans in order to make them look less tribal, and less stereotypical/offensive? Can you find a good lead who's a big enough draw? Will the general audience and the fans go along with whatever changes you eventually make, chief among them being the fact that you'll probably need to avoid calling your movie 'Black Panther' in the age of political correctness? Most importantly (to Marvel), will you be able to make a significant profit off of a film which will definitely cost a good deal of money, and is a HUGE risk.