It won't be. Matthew Fox has already mentioned (I believe back during Season 4) when he was on Jimmy Kimmel that he is one of the few people that the producers have told the whole storyline to and how everything will end up and he's part of it.
Not only that, but on the fifth season blu-ray/DVD commentary, Lindelof says they thought it would be cool to have Jack be passive for most of the season and let other people tell him what to do to, in his words, give him a break before what's coming for him in the final season. So Jack's definitely got a big role coming up.
Another hint of what's coming from the commentary -- According to Cuse and Lindelof, Desmond's purpose has yet to be revealed. Why he's special and "the rules don't apply to him" isn't specifically stated, but Cuse mentioned the turning of the key and being at ground zero for the hatch implosion, implying this is the reason.