Batman retired coz he fucked his leg up in the final scene of TDK, plus he feels Gotham no longer needs Batman.
Selena Kyle's under Bane's thumb, and comes to warn Bruce.
Bane's workin for, on behalf of, or is now leader of the League of Shadows, and comes to Gotham to finish Ra's al Ghul's work.
He fucks everyone up (including Bruce), and shit spirals into chaos like it did in KnightFall.
Bruce escapes, fucks off abroad to "retrace his steps" in order to "re-become Batman", returns to Gotham, gets a hand from Lucius to get better equipment, convinces Catwoman to join him, they fuck up a loada bad guys, and Batman beasts Bane in the end.
Maybe he reveals he was Batman all along to the public, maybe he retires, maybe he even passes on the Mantle of the Bat, who knows? (...except for those who've seen it, obviously)
All I can say is that this one looks so far removed from Batman Begins (I understood why they did it for TDK), it seems less of a Batman film and more of a "guy wearing a Batman suit" film.
Either way, I ain't lookin forward to it.