The addition of Bonham Carter -- who in addition to being nominated for an Oscar for 1998's The Wings of the Dove is a five-time Golden Globe nominee -- would bring a prestige element to the summer tentpole.
Principal photography started last month in New Mexico, with the hopes that most exteriors will be shot before a potential SAG strike. Warners is scheduled to release the action film in May.
Terminator Salvation was released May 21st, 2009 and stars Christian Bale, Sam Worthington, Moon Bloodgood, Helena Bonham Carter, Anton Yelchin, Jadagrace, Bryce Dallas Howard, Common. The film is directed by McG.