Given the way things are going, the title of the Series final episode, and certain barely remarked upon issues, my suspicion is that all of the lostaways on the island, along with everybody or nearly everybody else there, dies either this episode or the next - before (or maybe right at the start) of the final episode.
Things keep bugging me that don't quite fit with most of the 'end' scenarios described thus far:
1) First off, we have Hurley and the dead people. He doesn't seem to have displayed this ability in any of his pre island flashbacks, and all of the dead people he's seen - except for Alperts long dead wife, which I am inclined to think of as suspect - died on the island, and are presumably trapped there in spirit form, for want of a better term.
2) Second, we have Jin and Widmores top female flunky (who, I suspect will be communicating with Hurley via the spirit world in this next episode or the one after). Almost the very first thing she started grilling Jin about was the 'energy pockets' on the island - apparently because he mapped most of them in the 70's while looking for Jack, Kate, and the rest. These energy pockets are what make the island unique (apparently). (Side note - it might have been Jin's surveys that determined the placement of both the Swan and Orchid stations). Draining one of these energy pockets (the one under the Swan) let the island slip into the 'real world' for a short while. What happens if they are all drained in a similiar manner (not blown up with a nuke)?
3) the combination of 1 & 2 implies that the 'energy pockets' are what keeps the trapped souls on the island. However, as witnessed with the demise of Juliet (and probably the traumatic experiences undergone by the 'flash sideways' lostaways) those who die on the island or who enter into near death states or some such, become aware of the alternate reality, though they cannot enter it and their influence there is minimal at best. I would also suspect that these energy pockets are not just trapping the dead souls on this island, but are also somehow sustaining them.
4) This, in turn, brings us to the Man in Black. Given his abilities and claims...I find myself wondering if he has not, in fact, been dead for a very long time, that he is in fact simply a very old and very powerful spirit creature - maybe the first to die on the island or some such. Does his existence depend somehow on these energy pockets? And if so, is he aware of this? He might be arrogant enough to think otherwise.
5) Then there is the original and now dead Locke. Where did his spirit end up at - released to the afterworld off the island? Or trapped on it somehow? I suspect this question will become of crucial importance.
6) For what it is worth, I figure we are looking at one more extraordinary time travel session - a lostaway or three will venture back to the time Jacob and the Man in Black first arrived on the island to understand what really happend and what is really at stake. This might be the next episode, or it might be part of what the series final episode revolves around.
7) I also excpect the 'flash sideways' timeline will catch up to the current one in the series finish episode: Locke will be able to walk thanks to Jacks miracle surgery; Kate and Sayid will have served enough of their time to be released or parolled, ect.