Ok, so it was Michael as the Man on the Boat, and at least Sun was one of the remaining Oceanic 6. I question whether Jin actually made it off the island, because the flashforward turned out to be a flashback (see ticked off rant below). While you could argue the tombstone in Korea means he did, they could just as easily just purchased a tombstone for him even if he died on the island, just so Sun would have somwhere to go.
One thing that ticked me off about this episode was that Jin's was a flashback (i've only been married two months), Sun's was a flashforward. Now, in the past, the flashbacks were always used to give insight into the person's past or character.
THERE WAS NO FRICKIN POINT TO JIN'S FLASHBACK, WE ALREADY KNEW HE WORKED FOR PAIK AND WAS A DEDICATED WORKER. The only purpose to mixing up the flashforward and the flashback was to screw with the viewers, to get them to think Jin was still alive and he was trying to get to the hospital. That's just stupid writing.
Ok, quick question, because an earlier episode doesn't make sense now. Who's funeral did Jack go to in his first flashforward (end of last season)? The funeral director said no family and no friends showed up. When Jack met up with Kate, he asked her if she went, so it had to be someone they knew in common. But Kate acts like, why would i go to that jerks funeral?
Of the Oceanic 6, Sun lived in Korea and Kate wouldn't have acted that way. Sayid probably would not have had a funeral in LA and Kate wouldn't have reacted that way. Hurley would have had family there and kate wouldn't have acted that way. Jack is alive, and it's obviously not her. That's 5 of the 6.
I guess the answer lies in whether Jin is one of the Oceanic 6. If he is, then there is no answer to this question. If he's not, then that leaves the option that an additional person makes it off the island and Kate would call him a jerk when she found out he died. Sawyer, Michael, or Locke seem like they could evoke that reaction. Though only Michael seems likely to actually leave the island.
I suppose it still could have been Michael's funeral and if he assumed an alias "Kevin" when he got back to the states, no one would consider him a member of the Oceanic 6. Kate would definitely have that kind of reaction to Michael's death. But what about Walt? Wouldn't he have been there?
Michael keeping the name of Kevin would leave open the possibility of another of Oceanic 6. Unless Aaron filled that role. But if Aaron filled that role, then that essentially requires Michael be the one who died, but he kept his alias name and did not leave the island as one of th oceanic 6. But then where is Walt?