Is Sicario an adaptation? I can't find any reference that it is.
Also, Prisoners is technically an adaptation of a short-story, but it's a not very well known short-story (I don't even see a name for the story on Wikipedia) from the writer of the screen play, so you could make an argument that the short story is essentially just a first draft of the script.
I do agree that we should just let him continue doing whatever he wants, he's done excellent work.