I spotted this over on IGN but apparently a trusted industry source for Batman-on-Film claims that it is going to take a herculean effort on the part of Warner Bros. to sell Nolan on doing a third Bat-film, confirming an old rumor that the studio has indeed complied a short list of replacement candidates. So why is Nolan reportedly iffy on directing the film?

"The death of Heath Ledger in January of 2008 rocked Mr. Nolan hard. So hard that Chris was convinced that TDK was going to be it for him and Batman on film," according to BoF's source, adding that the Joker was envisioned as the villain in the third film.

The source also informed the site that BoF is "correct in reporting that (Nolan) is developing story ideas with [Jonathan Nolan] and David Goyer, but it will be until AT LEAST 2012 before we see the Caped Crusader back [in theaters]. And that is only an EARLY ESTIMATE at best right now. They are even saying it might not be until 2013."

BoF's source went so far as to say that, as of now, there is no story for Batman 3.

(Source - IGN / BoF)