Giacchino apparently said in an interview the other day that he was so excited about working on Batman that he's already composed the central theme for the film and sent it to Reeves for additional inspiration on whatever last minute script touchups and work while filming the movie next year. Bear in mind that Giacchino's been teasing his involvement on the film for a few months now, so I highly doubt he just wrote it up over the past week.
So yeah, it sounds to me like this particular score will be a big focus for Giacchino.