Which is silly really. Level cap is not what the game needs. It's just something to satisfy the gamer hunger for continued gameplay and gameplay can just as easily be obtained with new content balanced for the highest level.
I like the way Guild Wars had this figured out. Levels 1 to ~15, just building up through the n00b areas learning the game, ~15 to 20 finding out about challenge, and then at the level 20 cap, most of the game.
The Borderlands DLC 3 announcement reads to me like this: Pay for Playthrough 3. To be honest I have no idea what will be in it at this point, but after the debacles with the DLC thus far I'm not holding my breath for it.