Downey Jr has been long attached to star in Jon Favreau's upcoming Cowboys & Aliens. Favreau and Downey Jr has formed a dream team that inspires the success of Iron Man and its upcoming sequel coming this May, but the partnership will not going onto the new project.
Downey Jr is no longer attached to star and although no official reason was given yet, LA Times was quick to speculate that Downey Jr's departure may be due to recent heavy shooting schedule that has included the first Holmes, Iron Man 2 and Due Date. The other rumour that is possible was that the star has signed for the Sherlock Holmes sequel.
Nevertheless, Jon Favreau still remain as the director and the studio, DreamWorks will need to find a replacement for Downey Jr. Cowboys & Aliens will be a studio adaptation where it tells the story of Zeke Jackson, a gunslinger who must work with his Apache enemies to battle a horde of invading aliens intent on enslaving humanity.
The studio is still aiming for a release on the summer 2011.
SOURCE: LA Times, Slash Film and Empire Online