Director Christopher Nolan is saying he will not bring back the Joker for Batman 3 or any other Batman movie he's associated with. He tell's Empire magazine this;
“No”, says Nolan emphatically and unhesitatingly. He resists elaborating simply because, quite understandably, he says, “I just don’t feel comfortable talking about it”.
Nolan is a cool character and I'm glad he respects the character Heath Ledger made his own! If Ledger was still alive I'd be all for it but let's not do it. We have plenty of villains in Arkham Asylum just dying to escape and take on the Caped Crusader! Batman 3 releases July 20th, 2012.
If they want the Joker's presence to be felt let's introduce Harley Quinn, she's a fan favorite!