Okay, Jacob brings candidates to the island to replace him but so far no one has (and we don't know yet if Jacob was a one-time candidate to replace someone else). Jacob is there to keep MiB on the island. He has no other purpose than to keep MiB corked up on the island by the island. So if at the end of LOST MiB is destroyed or otherwise killed, there is no reason to replace Jacob. Therefore, MiB cannot be killed in the course of this contest he must be contained and a new Jacob take over the title of Cork Master. I don't know what this all means but my head is whirling.