My personal pic for Taila would be Emily Blunt but since she was already heavily rumored earlier in the year for Selena I doubt she'll be considered. She's also passed on previous comic book role offers so it's possible she's not interested in doing a comic book movie.
I honestly have trouble imagining an actor who would turn down a role from Chris Nolan in his sequel to The Dark Knight. Not after the money and buzz and awards and all that it won.
Short of Bob Redford or some such.
Certainly no young non-40 year veteran actor would be dumb enough, not post-TDK. Pre TDK? OK, sure. Post? You'd have to be brain-dead.