The ending of "Terminator Salvation" will be a big surprise after all. Moviehole reported that a Warner Bros. insider has claimed to have seen the McG-directed action thriller and stated big changes have been done to it over the past few months, resulting the third act of the film to be completely altered.
The changes to the ending of the movie starring Christian Bale and Sam Worthington were made reportedly due to the script leak back in 2008. The source further revealed that the new ending has tested quite well and "it's gotten a much better reaction than the 'big reveal' in the script did". On the new ending, the source was quoted as saying, "A complete  from the original film. Works better. Probably not as hard to swallow. Real good though."
In June 2008, Ain't It Cool News broke out that at the end of this fourth "Teminator" movie, John Connor will be seen fighting a T-800 and losing the battle. Feeling that it's important to keep the image or idea that John Connor is still alive, the top resistance people "rip off Marcus [Wright]'s skin and put John Connor's on the skeleton so now Marcus is John Connor."
Set in post-apocalyptic 2018, "Terminator Salvation" follows a stranger whose past could not be justified, Marcus Wright, as he joins John Connor, the man whose fate is to lead the resistance against Skynet and its army of Terminators. With Christian Bale and Sam Worthington taking the pivotal roles, Moon Bloodgood, Common, Anton Yelchin, Bryce Dallas Howard and Helena Bonham Carter will be seen among the cast supporting them. This Warner Bros. film is slated for U.S. release on May 21.