I REALLY don't understand when people say this. "Why redo the Joker". There are just SOOO many things wrong with that question. Lets get to them!
1. How could you NOT have the Joker in these films??? He IS Batman's nemisis. He is his complete foil, his polar oppostie. Not only is he probably the greatest villain in comic history, but the relationship he shares with Batman is without a doubt one of the most unique, interesting and complicated relationships found anywhere in fiction (comic and otherwise). Which leads me to my next point...
2. This isn't a redo of Joker because "The Joker" as he is, has never BEEN DONE. Burton gave us 2 GREAT Batman films that I love dearly, BUT they were BURTON FILMS NOT Batman Films. He had never read the comics and wasn't interested in making a "Batman film." And that's O.K., he's an artist that has a vision and I LOVED what he did. But when it came to Joker, he didn't give us JOKER. Joker isn't funny, he's nuts. He's sadistic. And the greatest aspect of the Joker is his relationship with Batman. Their co-dependance. Their inability and lack of desire when it comes to erasing the other. Without Batman, Joker has no point, and quite possibly without The Joker (and his other worthy foes that compose his Rouge Gallery), Batman may not have a point (one of the greatest aspects of Batmans psyche... does his presence perpetuate and create the madness around him....). Nolan is going to give us another BAT FILM, and for the first time in Live Action, we are going to get THE JOKER! And we're going to see Batman and The Joker duke it out both physically and mentally like the titans they are!
3. And yes, that does mean they can use any of the characters. That is why Penguin is rumored to be in "The Dark Knight" and that Two-face will be featured largely in the third film. But that doesn't mean we are going to get the same characters duplicated. Joker will be like he is supposed to be and the Penguin won't be a 1/2 creature with flippers for hands. He will be like he appeared originally, a short, aristocratic gentle-man with a lust for lawbreaking. I only hope he comes complete with an eye glass and a fondness for umbrellas ;-)