By the end of season 4, only four people know of Jack's true fate: David Palmer, Chloe O'Brian, Michelle Dessler and Tony Almeida.
According to a proven "insider" who posted at the FOX 24 Forum, a line involving Jack asking Palmer to check up on Kim was cut.
David Palmer: Jack Bauer would never compromise national security.
Walt Cummings: As much as I'd like to believe that... everyone breaks.
David Palmer: What you believe, is irrelevant!
Chloe: What about the autopsy?
Tony: There isn't going to be an autopsy! They wanted Jack dead, now he's dead!