*SPOILERS*
So... why do you think Desmond ran Locke down? My first guess was that he wanted to give him a life/death experience that, like Charlie, would cause him to see/remember the other timeline. Me? I'd rather make-out with Libby at the beach... but whatever.
My workmate thinks that Desmond, somehow, is bringing them all to the Hospital. Jack is there, Jin/Sun are on their way there, maybe Charlie is still there, Claire, perhaps Sawyer is taking Kate there. It sort of makes sense.