Next month's issue of Wizard Magazine gives some major spoilers for Iron Man 2, including the events that isolate Tony Stark/Iron Man, and the question Nick Fury asks Tony which he can't answer. Spoilers below...
Jon Favreau says the new movie is darker than the first, but not as dark as you'd expect — it's definitely not as dark as the "Demon In A Bottle" storyline, in which Tony grapples with alcoholism. Instead, Favreau says Tony struggles with "his own identity in the face of being a larger than life character who is. in fact, saving the world." Ivan Vanko, aka Whiplash, is indeed a combo of Whiplash and the Crimson Dynamo in the comics, and that primitive harness you see him wielding in the clips and promo pics is, as you'd suspected, just his first stab at creating a new technology.
The film opens with Iron Man's mood and armor both "grimy and ragged," in the middle of a major struggle that's not going well.
And it sounds as though Sam Rockwell's industrialist character, Justin Hammer, talks Tony Stark fan Ivan Vanko into hating Tony. And Hammer makes the War Machine armor for Rhodey, who's on the outs with Tony. And Don Cheadle says that if all goes well, there'll be a third film with the same cast, but he doesn't expect there to be a War Machine spin-off. (And Favreau says that they considered having ScarJo play a different role in the film than Black Widow, that of Wanda Maximoff, the Scarlet Witch.)
Most of all, the theme of the second movie is that "no man is an island," says Favreau, who says Tony realizes he needs other people. Adds Robert Downey Jr., at one point, Nick Fury asks Tony what it's like not to have any back-up. Tony faces issues that are more pressing than survival and more complicated than even his mega brain can handle.
Separately, a screencap from the most recent trailer shows what could be the "Extremis" enhance from the comics, which turns Tony into more of a cyborg and gives him a second skin and more of a healing factor:
Note also that in the scenes in the trailer where Tony seems to be fighting War Machine, his armor's central light is more triangular, along the lines of the Extremis armor in the comics. [Comic Book Movie and Comic Book Movie via DailyPop]