Bryce Dallas Howard is now in negotiations to replace Charlotte Gainsbourg in "Terminator Salvation: The Future Begins." Gainsbourg was just confirmed a few weeks ago to be the wife of John Connor played by Christian Bale.
But the actress had to leave production because of feared scheduling conflicts with another film, a French comedy over possibility of comminting to Terminator and being affected by the up coming actors strike which would see production stop and restart at a later date which could potentially affect the French film. The Hollywood Reporter article can be found here.
Production has already started on Terminator Salvation: The Future Begins directed by McG, is already underway in New Mexico.
