I'm intrigued to see Gabriel Luna as the new Terminator, but did they have to have Arnie in this one? Is there some sort of unwritten rule that Arnie must appear in every Terminator movie? (I know he wasn't in Salvation, but there was the CGI version which I suppose kind of counts).
Arnie and Linda are the two people who made the movie so yes, he HAS to appear in these films.