And as I said, they cant admit they know Desmond without adminting the island wasnt deserted.
They cant bring Desmond back because then people would be all "WTF, this guy wasnt even on teh plane"
Plus evil Alan Dale will probably still want Desmond dead, so easier for him to beleive he is, while he and Penny live it up on the island.
Maybe those two turn out to be Adam and Eve (the skeletons)
OR if we find out the Desmond loves me instead of Penny, and he's flying here RIGHT THIS MINUTE, to take me away to his secret island hideaway.
Who IS Desmond talking to in that trailer?