I've read that initially they were setting it up for a Michael-Sun relationship but now they like the friendship developing between Michael and Jin. So maybe Jin's days are not numbered. On the other hand, I think Jin might still be a good candidate for going, just because I think some of the other characters are more important/compelling. It's hard to think of who is going to go and who is going to survive though!
Oh, by the way, I was reading an article somewhere, and the creators were saying that the survivors would eventually get off the island...if it is indeed an island. I think they were just kidding, but you never know.