So it was a bit of a curveball when information started to come out about the film and it all pointed toward a more personal, self-contained story about Tony and his nearest and dearest.
The filmmakers have also pretty consistently referred to it as a "techno-thriller," something that doesn't really fit the established tone of the Marvel Cinematic Universe perfectly but does make sense for Iron Man.
In a new interview with Wired (you can see video at the link), director Shane Black and star Don Cheadle got into some specifics.
“We had kind of a conundrum in that The Avengers opens up this huge sky-hole full of interdimensional aliens. You kind of look back and [think], ’Well, what do you do after that?’" Black explained. "Except go back to a sort of more gritty, intense kind of techno-thriller root. You just go in and you sort of wrestle...you've got to jerk things around a little bit, and mix it up so that there's still more story to tell. And the way you do that is treat it like the first two [movies] were part of an ongoing story that hasn't finished yet. The journeys are all mythic in a way we recognize from a lot of years...mythic superhero stories. Today's world is so complicated that the simplicity of myth has come back around the desire, or need for people to feel and see that that's unprecedented; given how just confusing the world is right now.”