I agree that #4 will be Sayid.
I also think that Kate and Jack end up together and can't make it work off island and this is part of the reason for Jack's fall into depression. His call to her in the finale was too familiar.. "Hi, it's me." Thus I don't think Sawyer is one of the six..I just hope he doesn't die.
Jack's call to Kate was whiney because Jack's always been whiney, and a cry-baby. Jack, Kate and Hurley made it off the Island because they all would compromise their principles just to get the f off. Consider who was left:
Sayid? Sayid's dead and was willing to face his maker, unless Nadia shows up--then it's game on. If Nadia works for Dharma, which is a very very strong possibility, he'll stay with her. If not, Sayid has nothing to return to, like most of our Losties. Actually, all of them.
Sawyer will bite it. He's too proud a man and I don't think he'll make it off the Island. Ben was right, Sawyer has nothing to return to. The only thing keeping him alive was looking for the man who killed his mother and father. Well, he killed that SOB on craphole island <story done>
Locke -- left behind and wanted it that way, no matter how the tides turned.
Jin - imho, a totally different character than we know and he'll probably survive, but put his wife on a heli or plane first to leave.
Sun - don't f with Sun; I still believe she killed her lover from the hotel and when push comes to shove, she'll protect fiercely like a caged rat. (oops, did I say that? Reminded me of a Skinner Box rat)
I don't think Rose and Bernard leave.
and here's the kicker.....
I think the flash forward we saw at the end of S3 was a flash-flash forward. It is a child in the coffin, unless someone was put into a woodchipper by their accomplice beforehand, which is highly doubtful.
I believe Kate has to return home to her son, hence the "he" and "him" reference, but is the child hers, or is it Sun and Jin's? Sun trusted Kate enough to tell her that she cheated, she thought she was preggers, etc. Did Sun and Jin die and Kate took their child to care for him, or is it Aaron? Whomever kate had to return home to, it was not a lover--I believe it is a child.
and on a personal note: I wish the Marshall would've made it. I liked him.
speculation cheers
*Des8
PS* wouldn't you FREAK out of Shannon and Boone were two of the Oceanic 6? heh heh