Helena Bonham Carter in talks to join the cast of Terminator 4.

AccessHollywood.com reports from an unknown source the star of Fight Club, Sweeney Todd and of course Harry Potter, as Bellatrix, is in 'serious' talks to play the lead villain in 'Terminator Salvation' which is being produced by Warner Brothers.
Treat this as a rumour for now until confirmation is received officially, but lets hope its true and She joins Christian Bale (John Connor) in the line up. Its sure to be better than T3 then!