Or at least the major plot points are.

They probably need McKay for dialogue, character stuff, and maybe action sequences. All of which I have faith in him to deliver.

I know people say the current post-Wright draft is trash, but I'd be willing to bet Marvel knows what story they want the filmmaker to tell, and they're just looking for a voice to deliver their story. I bet Wright wanted to tell his story his way, not their story his way. And despite the PR hit they've taken, I trust Marvel from an overall storytelling perspective.