Major film magazine Empire has a massive Christopher Nolan-centric issue coming out shortly (mostly for Inception), and Obsessed with Film got their hands on a copy early.
In it, Nolan very clearly lays to rest any rumors that the Joker would make an appearance in the movie. When asked if the Joker would appear, possibly in Arkham pulling the strings for some new villain, Nolan replies “No!” and “I just don’t feel comfortable talking about it.”
The third untitled Batman movie releases July 20th, 2012. Warner is expected to reveal more at next month’s Comic Con in San Diego.