But I am not convinced that he is "dead" in the flashforward. Only the Ocean 6 are considered survivors, anyone not counted among the six would be dead to the rest of the world. I think Jin stayed behind for the same unknown reason all the others did. He said he would do anything to keep Sun and the baby safe. I think the gravestone would be ceremonial to cover for his remaining on the island.
I like that thought. Why would Hurley take her to the cemetary though unless Sun was being watched all the time, there was that guy outside her hospital room. If her father thought Jin was dead he might still have a bodyguard for her since she was now so famous.
So do you think the Hurley stuff was before or after Jack saw him in the looney bin?? I think it would be before because Aaron was much older (maybe 2) and Sun was 3 weeks from the middle of the trimester so the birth was about 4 months later. The editing on that final sequence was awesome!