Similarly, I have yet to see the movie, but I know that the film tackles various magical and genetic stuff that isn't typically dealt with within the Iron Man comics themselves - the Avengers franchise tackles such things AND the hero teamups, but the individual series do not cross over nearly as much in such themes. So, in sticking within the Iron Man movie world, you can expect NOT to see a Norse God or a big green guy whose strength increases with how mad he gets - not IMPOSSIBLE feats to explain in a sci-fi setting, but one that Iron Man does not deal with himself.
Extremis has already been adapted in the "Armored Adventures" animated series, but not nearly to the same extreme (pun intended) that it was presented in the comics. I hope the writers find a way to believeably incorporate Extremis into the Iron Man movies without it coming off looking like magic. Comics can get away with that as the nature of its medium; IMO a live action film needs to take a more realistic (looking) approach to sell it.
Still, the Extremis arc in the comics is popular because it crafted a very good story to go with the technological rebirth of Tony Stark. It seems that Mallen will not be part of this movie, though Maya Hansen and Aldrich Killian are; and with the Mandarin seemingly a part of the story (seriously, who else can Ben Kingsley be?) I hope Extremis will tie them together rather than be just the next gimmick Tony comes up with to get a cooler suit.