Jack's a fighter, yet he relented for the Others, for ben really, and Ben rewarded him with information(and the false hope of leaving). Jack seems to know what's up, and now that he knows, will we ever see him back at the beach again? Will he ever be allowed to leave Othersville, will he even live through the series? these are the questions we should be asking.
Even Juliette couldn't tell Jack the deal, because once you know, in your heart, that the island itself is incomprehesable, you really can't tell anyone else. Not that you wouldn't, you just don't know how to start a conversation like that.
"Imagine a molecule on a blade of grass, now imagine you live in it..."