Since there are only four candidates left, this is probably the most likely conclusion: Jack replaces Jacob, Sawyer replaces Locke's role, they are enemies already, so the circle continues, keeping good and evil in balance. Kate's name was crossed out on the wall in the cave, Hurley, though good, is not leader material, Sun idk, she hasn't played much of a role, neither has Gin. (thats five candidates?). In whole season starts looking through Jack's eyes, and i bet it will end that way.