This war against crime, this personal vendetta, it's far more than him getting over his parents. He wants to follow in his fathers footsteps, he knows ra's had the right idea at first, It's not about vengence anymore (this is explain in BB) it's about saving gotham city just like Thomas and Ra's wanted to do. As long as Gotham needs a batman, he will be batman, the only way he willingly stops is if Gotham doesn't need him anymore. He won't leave a gotham that needs him...certainly not to someone else. What will he do then? Go off and make babies with Selina, while crime continues to run rampant? "oh its ok, i don't need batman anymore, I'm over it, blake can deal with that mess now"
If he goes out alive or dead, we will leave gotham a much much better place than we saw it where men like gordon and blake (as a cop) can easily manage whatever goes wrong.