Originally Posted by The Joker
Could have but didn't for several reasons;
1. The movie says Batman's not been sighted since the night Dent died
2. Nolan said the 8 year gap was representative of Batman's retirement
3. Nolan says on the special features of the blu ray that the injury he sustained that requires a cane is from the fall he had with Dent at the end of TDK. Can you see Batman being active in crime fighting with an injury like that? You see him limping away at the end of TDK when the Cops are chasing him. Clearly the injury just deteriorated over the 8 years.
Whilst I definitely like the idea of Batman fighting on for a few more months, there's obviously more proof in the movie of him retiring the night Dent died than the opposite. How anyone can deny this is ludicrous