I think there are three major likely endings regarding Batman's fate at the end of the film:
1. He dies-This is the least likely, but with WB already all but confirming a reboot after Nolan, this would at least mean they MIGHT let Nolan kill him off if he wanted to. Sacrificing himself for the city makes Batman a legend and a symbol, which is what he set out to do in Begins.
2. He "dies"- Bruce survives but it appears to Gotham that Batman died sacrificing himself for the city. This has the same effect as scenario 1. Therefore Bruce retires allowing Batman to remain a symbol.
3. He lives- Batman becomes the legend and symbol at the end, regaining Gotham's love and trust, but Gotham still needs him. He has now reached the status as Gotham's Protecter that we know of from the comics. The film ends with a scene that makes it obvious that Bruce is still Batman and will be for a long time. This also could be a fitting end for Nolan's trilogy because the trilogy was about Batman's beginning. We've seen him reach his legendary status and now this chapter in Bruce's life is complete.
I honestly don't see it ending with Gotham knowing Batman is still alive, yet Bruce still retires.