Because, at this point, especially since Sun was shot in the flash sideways (), I don't think they're going to be reunited. Or, they will be, briefly, and one will die (betting on Sun).
Too much is pointing to that they won't get back together. Like Keamy! "Some people aren't meant to be together."
The producers already said they won't explain the numbers (more than they already have). Basically, the numbers are 4 - Locke, ... etc. That's all we're getting. So they say, anyway.
"minor spoilery as to why desmond is on the island and stuff'Desmond is there, basically, because Widmore brought him there. A sneak peek was released with a scene explaining that (how he got there). As to why he's there, it might be explained (but I doubt it, at least not yet).Next week is Desmond, and I like Desmond, so it should be entertaining. My guess though is that will take the entire episode to tell us why he is back on the island and the rest of it will be his misadventures in alternate reality LA and a lot of 'I'm going to tell you exactly why you're here...' *interrupted by gunshots*.
Set photos show desmond in some (SPOILER)weird Room 23-esque room, and then some other (younger) man is in the room. I'm guessing it's a room that sends people back in time but keeps them in the present.
Oh, and these people are "confirmed" to die: (SPOILER)Widmore, Ilana, Sayid, and Sun.