“I didn’t mind wearing the suit at all. I thought it was light and perfectly comfortable and my children thought I was extremely cool,” Paltrow said in an interview officially released by Disney, meaning that even the studio doesn't consider that plot point a spoiler.
What's more interesting, though, is looking back at the first trailer and some early teaser images, then comparing them with more recent material, it appears as though someone takes Pepper hostage in the film (which we knew) and subjects, or attempts to subject, her to the Extremis virus.
Pardon us if you've heard this one, but while I can't be the first to have thought of this, I haven't seen the theory verbalized elsewhere yet.
Take a look at the photo above and the one at left; the top photo, from Iron Man 3's first trailer, shows Pepper Potts in some kind of arcane restraint device that didn't have much meaning at the time. The photo at left is of Aldrich Killian's Extremis soldiers, apparently being treated with the techno-organic enhancements before they're sent out to battle.
Of course, the question becomes what's really going on there. If she's being treated with Extremis against her will, it shouldn't take long before the enhancements that treatment grants her puts her in a position where she could easily overpower her captor and escape. Could it be that she's undergoing the treatment willingly--that we misinterpreted her plight all along and that this is actually part of an attempt to reconnect with Tony during the point in the movie where he's missing in action?
If she is being subjected to some kind of experimental treatment, why? Is Iron Man's girlfriend really an ideal guinea pig? Rich, pretty white girls' deaths don't go unnoticed, particularly when their boyfriends are superheroes and their day job puts the in touch with the largest, most powerful covert ops organization in the Marvel Universe.