Maybe Travis Bickle was dead at the end.
The other day I said that filmmakers should not explain their movies, and screenwriter (and brother to Christopher) Jonathan Nolan has taken that to heart. In an interview with IGN, Nolan refused to shed light on the ending of The Dark Knight Rises, which has engaged the over-analyzing minds of millions of Batfans who think that Alfred is hallucinating Bruce Wayne in Italy.
That interpretation makes no sense narratively (it's revealed the Batplane had its auto pilot fixed), and is not held up textually - nothing about the scene indicates dream sequence or hallucination, as Bruce's vision of R'as Al Ghul does - but there are some people who need the ending to be grim n' gritty through Bruce's death. Bruce doesn't die. He quits. Again. The Dark Knight Rises is about a superhero doing a revival tour of his character. It's like when The Who get together for a festival.
But good on Nolan for understanding that you gotta let the fans do their thing, especially when the movie you've made is so otherwise non-compelling.