Tonight’s ending definitely qualifies as “unpredictable.” The single act of Ben Linus dying would easily set off a series of events in which course correction could not totally overcome the effects of that one death. To wit: Ben never becomes the leader of the Others. So there’s no power struggle with Widmore. So Desmond never arrives on the scene. So Oceanic 815 never lands. So Jin can never go back in time to stop Danielle Rousseau from going into the Temple. So Danielle never, ever changes the signal from the radio tower, which explains why we heard The Numbers as Lapidus tries to land the plane on Hydra Island.
Now, the big question remains on whether Ben did or could even die in 1977, but if he did, Sun and Frank are in for a surprise on the island in present day.