[The_Return]

I think the main thing that points to Dent still being potentially alive is the confrontation between Batman and Maroni.

I forget the exact words, but Maroni says something to the effect of "If you're trying to intimidate someone, pick a better spot. From here, the fall wouldn't kill me.", to which Bats replies: "I'm counting on it", and drops Maroni about 2 stories or so.

Well, Dent's fall was from about the same height...