I'm pretty sure Michael is going to die on that island, because the island has an old-school sense of justice. Anyone rooting for him to live? Die elsewhere? I hope he dies a miserable death. No sympathy for him.
Tell us how you really feel, lol! Actually, yeah, I don't like him either. I think the funeral could be his cause, obviously, he has no one who likes him back home. Then again, like you said, he could die on the island. Maybe he'll die redeeming himself to the other survivors somehow.
My best guess for the coffin has always been Hurley, but my wife keeps pointing out the coffin wasn't big enough. I don't know about that. She's probably right. My second guess was Ben, because even though Jack hated him, by that point in the flash forward, Ben may have been his best and only shot of getting back on the island. That would explain by Jack was neither family nor friend and still felt sorrow at the funeral. It would also explain why no one else showed up.
I agree with your wife that the coffin isn't big enough, though that may not matter. I think a lot of who is in the coffin depends on the timing. After Jack went to the funeral home, he met Kate and told her they had to go back. Was that prior to him proposing marriage to her or after? I am guessing it is after and likely the most recent event in the whole series of things. So, if that is the case, then, yes, I believe it could be Hurley. Still, I would be surprised that none of his family would show.