This is the critical comment taken from his conversation with Entertainment Weekly...
Nolan: I must say that I’m glad — I’m very, very glad — to be embarking on the last chapter of our Batman saga without any sense of obligation or duty to the studio. They did very well with Inception. So I’m able to go into finishing our story in a very enthusiastic way.
That pretty much seals the deal, doesn't it? Now, bear in mind that he says "our Batman saga". This by no means suggests there won't be any more Batman films. It doesn't even really suggest Christopher Nolan won't have anything to do with any future flicks. He just won't be directing them or assisting with the script. You can bet Warner Brothers will continue on with the franchise in some way, shape, or form and will a way to keep Nolan involved even if it's just in an advisory role.