It turns out that Warner Bros. had pitched a fourth film Dark Knight. Bale told the Toronto Sun that he rejected to proposal out of respect for Christopher Nolan's vision: “Chris had always said to me that if we were fortunate to be able to make three we would stop. 'Let’s walk away after that,' he said.”
"Then when they inevitably came to us and said, “How about a No. 4?” I said, “No. We have to stick to Chris’ dream, which was always to, hopefully, do a trilogy. Let’s not stretch too far and become overindulgent and go for a fourth," Bale explained.
Speaking on the lasting impact of the trilogy on the comic book movie genre, Bale revealed that he "literally had people laugh at me when I told them we were doing a new kind of Batman.” He speculated that the success of the trilogy lay largely with Nolan's take on the project; “we never were arrogant to assume that we had an opportunity beyond one film at a time.”