Jack DID do something similar to what Jacob did, though, at the beginning of the episode. In "What They Died For", before filling the cup with water for jack to drink, it showed Jacob squatting down near the stream and him placing his own hands into the water, cupped a little water in it, then let it fall from his hands and rubbed his hands together just a little, almost as if he were washing them. At the beginning of "The End", it shows Jack squatting down near the stream and bringing his wet hands back up as he just looks at them. I remember thinking it reminded me of what Jacob did before he gave the cup to Jack. So, maybe possibly Jack knew all along that he would eventually end up making Hurley the new island protector and was shown doing the same things Jacob did before the point of transition.
Afterall, when Jack was telling everyone to get to the plane to leave the island and Hurley said he was going to stay with Jack, Jack just smiled and let out a quick laugh. He didn't try to convince Hurley to get on the plane like he normally would have done, and like he did with Kate...so maybe he didn't argue with Hurley because he knew Hurley staying was necessary??