Update 11/04/10: Exclusive update from Batman-News.com
Earlier this summer ComicBookMovie.com reported that Batman 3 would film in New Orleans. This rumor was quickly dismissed, as ComicBookMovie.com has been very unreliable in the past, going even as far as publishing a fake Christian Bale interview. Batman 3 will still probably be shot in the UK and Chicago like the two films that came before it, however sources are now saying that New Orleans is a likely location, due to tax credits. To add more fuel to the fire, Acting-Auditions.org has Batman 3 casting calls listed for New Orleans, LA, and Chicago.
Update: Backstage.com has more specific details on the New Orleans casting call:
Batman 3 (Action/Comic Book) The third installment in director Christopher Nolan’s Batman reboot. Christian Bale, Morgan Freeman, and Michael Caine star. Casting: John Papsidera, Automatic Sweat, 5243 W. Washington Blvd., L.A., CA 90016. Shoots in April in New Orleans.