From what I gathered from the trailer, in order for Sarah Connor to be that future-savvy by the time Kyle was sent back, she must have had her first contact with a Terminator years before that point. I'm guessing the older-looking Schwarzenator was sent back to protect and mentor her when she was much younger, and that he's allowed his external appearance to age naturally since that point in order to blend in as a human.
EDIT: Sorry, misread your post as "I hope they came up with an explanation".