Redemption. Perfect theme.
Lots of villans? You bet! Never been done since 1966 and that was silly. Time to do it up right.
Catwoman, a night prowler that only Batman ever sees. She makes news, but no one else ever sees her, only Batman. For the public, maybe fleeting descriptions, but no photos. And it ends with Batman/Bruce never knowing who she really is and she helps him after some finale, and he can't find her again. And she is not all bad. Something kinda sad or forlorn. Haunting even. Her story could almost be a minor subplot aspect.
Riddler, older actor. I actually originally thought of Terence Stamp, but then thought, no, why not go to someone Nolan has worked with. Either David Bowie, or go younger, and get Guy Pierce. And he is THE dangerous one of the plotline. The one Gotham City needs Batman's help with, openly.
Penguin, just a mob type, club owner guy, who hates his nickname and is one mean mutha. Worthy of Batman villain status. Think an older, fatter, shorter Michael Corleone type. Mean as hell. Must show up at least in a small role.
Ra's must return somehow. I think the chaos is all his doing. Ultimately. Be a great third act surprise.
Talia, love interest, but not gonna work out...be a good one though.
Scarecrow, back maybe...if he can be more.
Harley, maybe. Could be ok alone. Just in memory of the Joker. Was a fan. Has pictures of him around. Videos. Or, less likely, the recasting of Joker, but I sense what everyone else is saying, that would be incredibly unpopular. I rescend my idea of him being recast.
Bane? Nah!
Croc? I wish, but nah!
The Ventriloquist? Maybe. Kinda be cool with Nolan's love of magic industry imagery.
Two-Face is back? Maybe, but I am beginning to think he'd be redundant. He's done his best stuff already. No new territory other than new makeup, maybe more healed, and a snazzy new split suit, but not much else. More of same makes Harvey a dull boy. I say he doesn't show.
Mr Freeze? My favorite Batman villain, so of course I would be OK with it, but in Nolan's world, he would have to be just some nut that sprays liquid nitrogen on people, doors, etc., and is only dangerous, but not some blue "cold guy" thing. Just a nut with a nitrogen freeze gun. Unlikely he will show in this universe any time soon. Could though.
Hugo Strange, Dr Death, any of the mad doctors? Not too likely. Strange could...maybe....
More Maroni and assorted thugs? You bet! I sure hope so. LOVE Them being around.
Look for the return of the batsignal at the end, and an iconic Batman standing pose at the end, as he came at the camera in Begins, away from it in DK, and now, he makes his stand. Just a thematic difference in ending imagery.
Oh, and Batman goes grey and black. More traditional this go round.
More Dark Knight comics imagery. We won't see him much at first, hands through walls grabbing crooks, more sneaky stuff like his first appearance in BB. Cops after him like in Year One comic. That sort of stuff.
More scenes with Gordon in his office.
More detection.
BIG finale. Huge. Biggest yet.
Just some guesses.