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Sam Worthington to Join Terminator 4 Cast
http://firefox.org/news/articles/1192/1/Sam-Worthington-to-Join-Terminator-4-Cast/Page1.html
Crystal Carroll
Crystal is a 30-something writer living in Northern California. She divides her time between writing technical documentation (techy, tech, tech requirements docs), analytical essays on television shows that hold her brain for ransom, and the occasional bout of fiction (like plague, only with characters). She enjoys Pinot Noir, but not during robot apocalypses, and feels all movies could be made better if they had a Sleestack in the background. 
By Crystal Carroll
Published on 02/13/2008
 
According to Variety, Sam Worthington (Hart's War, MacBeth), having just completed his role in James Cameron's upcoming Sci Fi movie Avatar, was recommended by Cameron to McG, Terminator 4's director, for a staring role.

Cameron gives John Connor a hand with recruiting
According to Variety, Sam Worthington (Hart's War, MacBeth), having just completed his role in James Cameron's upcoming Sci Fi movie Avatar, was recommended by Cameron to McG, Terminator 4's director, for a staring role.

In Terminator 4, Worthington will be playing Marcus, who it's reported will be a main character over the upcoming Terminator trilogy.

The nature of Marcus' role in "Terminator: Salvation" is anyone's guess. Terminator 4 will be set post machine/nuclear apocalypse with John Connor, played by the ever interesting Christian Bale, leading the good fight. However, given that rumors have Connor being more the leader-messiah than the main character of the series, perhaps the various headlines of "Worthington to star in Terminator" are on to something.

http://www.variety.com/article/VR1117980831.html?categoryid=13&cs=1&nid=2562
http://imdb.com/name/nm0941777/