No, Scarlett Johansson will not be in Iron Man 3
Thanks to the unusually strong binding properties of the Jessica Chastain additive and the ballast of an increasingly beefy Gwyneth Paltrow, Iron Man 3 has expediently eliminated the need for Scarlett Johansson, who confirms to Screen Rant that Black Widow will not be returning for the sequel. With Chastain fulfilling the role of "sexy scientist" and Paltrow tackling "sexy former CEO"—not to mention possible supporting roles such as "sexy concierge," "sexy graduate student perpetually halfway through her thesis," or "sexy digitally removed homeless person"— the film has already achieved acceptable levels of sexiness, after all, with a surfeit of Johansson sexiness only gumming up the works. Besides, Black Widow already sees plenty of action in The Avengers, and Johansson has renewed her previously stated hopes that this will someday all lead to her own spinoff—a movie she believes could be a Bourne-type thriller, provided she can work up the gumption to "spend another three months shedding the manatee skin and squeezing back into that suit," because Scarlett Johansson is like a gross sea cow most of the time. Anyway, adjust your expectations of Iron Man 3's levels of sexiness accordingly.