The Dark Knight Rises

The movie ended with

 Spoiler

Bruce Wayne accepting that he himself isn't needed as Batman anymore, and that it's finally time for him to move on with his life, and as well as with Selina Kyle, they used the CleanSlate™ and started a new life.

Fans would devour Nolan alive if he directed that as a 4th movie. People are seemingly mad enough about this not living up to their expectations from TDK. It's very possible that there could be a 4th movie, but one with ***Hidden content cannot be quoted.*** would need the best script ever written to succeed past being a sellout.

 Spoiler

It's definitely possible, but it would have to revolve around Robin John Blake rather than Bruce Wayne. Bruce Wayne is done. People tend to forget that as ageless as superheroes are in comicbooks (cough parallel universes cough), they eventually will die/retire/get too damn old. Except Superman. That being said, there is a possibility there for a Justice League tie-in since it would step further into the future than these three movies, and could set up the plausibility for other superheroes/technology/MAGIC to exist, if Nolan wants it there.

DEM EAR GOGGLES

Yeah, dem goggles.

Also, I think thats one place DC has really screwed themselves. Their reboots are so inconsistent with the previous content that it really makes it hard to pull a bunch of movies together for a Justice League movie, like Marvel did for Avengers. Right now, Batman was the best they had done, and the Super Man movie looks like it could be decent, but it all is just too disjointed to really work out well in the end. A 4th movie would probably work best as a transition towards the JL movie, imo.