Not much going on in the comics movie world that isn't Watchmen-related right now, but word broke the other day that Leonardo DiCaprio will star in Inception, Christopher Nolan's first post-Dark Knight movie (and first movie in a while to not star Christian Bale). I'm sure it'll be interesting. And of course a few people have pointed out that many directors like to work with actors they know (consider Nolan's choice of Bale and Michael Caine for The Prestige), so they've started to think of villains DiCaprio could play. For what it's worth, I wouldn't completely mind him as Hush, The Riddler, or Black Mask. But he wouldn't be my first choice for any of them.
After The Scarecrow, Ra's Al Ghul, The Joker, and Two-Face, who should be Batman's next enemy in the Batman Begins/The Dark Knight series? Well, as of now we know that Tom Hardy will play Bane and Anne Hathaway will play Catwoman.
Check out the master list for all the villains covered. I've pretty much run out by now. Obviously, there are more Batman villains, but not any of significance that I know of. As of February 2009, no one is confirmed as a villain. Not the Johnny Depp Riddler, not Phillip Seymour Hoffman Penguin, nobody.