I'm not so sure we are done with the island, since we didn't see the 'rescue'. Locke was told by Walt that he had a lot of work to do, since Walt is now off island, a psychic himself, and knows the end, i doubt all locke had to do was stop Jack right then. We will be back on the island I'm sure, and we may not see future flashes again for a while, because we are just assuming Jack is acting the way he does because the Losties got off right away.
I think Jack has many a tough decisions left on the island, and because he didn't make the tough ones well enough, we saw how it ended. Jack may not have wanted more blood on his hands, and the people that are coming are probably far worse than the others and Ben. Hopefully Jack does not follow the ghost of lost future...