I think Michael and Jin are both alive. I really like the point made about it being Michael, Jin, and Sawyer being back in the water. "You can go now" can be interpreted a bunch of different ways. I know, I know. The most obvious one, since he was standing right next to the C4, would be that it was time to die. That just seems too strange for Christian to come announce Michael of his death. He could've just blown up, and that would have been a lot more believable. I guess there are other 2 possibilities. Perhaps he can go to his son now because he's redeemed himself a little. I don't think that's what was meant either. The island seems to always be trying to draw the Losties back to itself. I think Christian came to tell Michael that he can go back to the island now because there is more that he was meant to do.