So in the finale we learned that Locke is dead and that he was used by the nemesis. Thus we all learned that Locke is gone, what is to become of him?
Well i have been thinking; Maybe Locke's only purpose on the island was to get Jack to believe in Destiny thus ultimately save whatever needs to be saved. Jacob knew Locke was the one to do it, he just needed him alive long enough to do so. Locke has the faith, Jack has the willpower.
Maybe as result, even though Jack saved the island physically, it was Locke who saved the island spiritually.