I think I've made this observation before here, but to repeat: You cannot predict the biggest box office successes. A movie that does historic-level totals does so by having great legs and you only get that sort of repeat-viewership when the movie taps into, and becomes part of, the culture. And that's something you just can't predict.
If you're a studio chief, you can basically manufacture a film with the goal of making, say, $80M, or $200M. But there is no way of manufacturing a cultural phenomenon on purpose. Look at the all-time list adjusted for inflation. The one thing most of the movies have in common is that you'd never guess they'd be on this list on the first day of their releases: Gone with the Wind, Sound of Music, The Exorcist, 101 Dalmatians. You get my point. I think Dark Knight is going to end up on the un-adjusted top five grossing list. And I think it could become a phenomenon. But I wouldn't predict that.
Now on to the more interesting point. Galley Friend T.J. sends in a particularly keen observation. Spoilers Ahead!):
Here is something I immediately noticed last night upon viewing the film. Nolan has brilliantly inverted the world of Batman's past. Take, for example, the climatic scene where Batman and Gotham police try to save both Rachel and Harvey Dent. The situation neatly parallels the predicament that Batman faces in Batman Forever (a terrible film). In that film, the Riddler has captured both Robin and Batman's lady love. Batman/Bruce Wayne must choose which one he will save: his love, who represents Bruce, or Robin, who represents Batman. In the end he saves them both in a classic bit of heroism by diving down a seemingly never-ending shaft, scooping up both just in time, and explicitly proclaiming that he is both Batman and Bruce Wayne.
The Dark Knight turns that situation on its head. There is no option for Batman to save both Rachel (Bruce's love) and Harvey (Batman's sense of duty). From the first, he must choose ("Rachel" he tells Gordon, as he jumps on the Bat pod to save the day) and then when he does he is deceived by the Joker. He thinks he is going to save Rachel, but it turns out the Joker has reversed addresses on him.
But Rachel and Harvey die as a result. Rachel is, of course, killed in the explosion. Harvey is brutally scarred (emotionally and physically) even though Batman helps him escape. Harvey Dent as anyone knew him is now dead, with Two-Face taking his place.
This is probably over-thinking it. But I found this to be a neat parallel to Batman Forever. It shows Nolan's Batman does not reside in the same world as previous incarnations. He can't "save" the day in a classical sense. He is forced to make one impossible decision after another and even then he can still lose everything.