Kateliegh, it was clearly shown that Jin had an old cellphone, where Koreans are always way ahead of the curve tech wise. Jin may not be dead, but that was definately a flashback of his. Plus, if he did have to get back to his old way of life, that would be with Sun.
I bet Jin is still alive, and I agree with some thoughts that 'You can go now' is even way too vague for the show, so vague, that it could actually be NOT vague, as in, 'Hey Mike, you know this boat better than anyone, get to a side deck quickly and you'll be off here before the explosion'. But that's way too long, so Christian said, you can go now. At least, that's what I'm hoping happened. Everyone is always hating on Michael, I like the guy, he's had some hard ass luck.