First of the new guys up for the movie, revealed by Variety, is Guy Pearce, continuing his current trend of starring in sci-fi tinged properties. He will play Aldrich Killian, co-creator of the Extremis virus. Killian has a very minor role in the comic, only present on two pages, so expect his role to be bulked up in the film.
Bleeding Cool reports that Jessica Chastain (The Help, Tree Of Life) will be playing a "sexy scientist", their words not mine, who is "every bit as smart as Tony Stark". It is assumed her character will be a version of Maya Hansen, who created Extremis with Killian. The comic storyline reveals that Hansen and Stark had a relationship in the past, so this could put Chastain's character and Gwenyth Paltrow's Pepper Potts on course to hating each other.
Finally, Twitch reveals that Chinese actor Andy Lau (House Of Flying Daggers, Infernal Affairs) is in final negotiations to star in the film. Since the movie is being co-produced in China, Chinese backers Walt Disney China and DMG Entertainment want a big Chinese name attached. If Lau accepts, he will play a Chinese scientist and friend of Starks, who provides the billionaire with new technology to fight the Extremis virus. And yes, when I heard of Lau's involvement I immediately thought this would be the long awaited appearance of Iron Man's nemesis, The Mandarin.
Iron Man 3 is expected to have a world wide release on the 3rd of May 2013.