Batman 3

The sequel to Dark Knight, though most definately won't be called B3, is building momentum.

The obvious villain for this will be Harvey Dent becoming Two Face, a story arc that's been building since Begins.

Hugh Jackman was first choice for Dent, but he's off doing Wolverine. Ryan Phillippe is another choice. Liev Schreiber was mentioned, but of course he's now SabreTooth in Wolverine.

And we know Dent kills The Graysons and gives birth, as it were, to Robin.

The Penguin could make a future appearance, this time recast as a British arms dealer.
Philip Seymour Hoffman would be perfect for this.

Then there's Bruce Wayne's love interest Talia, daughter of Ra's al Ghul.

And we just have to see a rebooted Catwoman at some point!