I'm a little bit confused, although I have a feeling we're going to have to keep watching to find out to get an answer...But if Jack gets off the island (presumably from meeting up with the freighter people and leaving in their helicopter) along with Kate and Hurley (leaving three unknown of the Oceanic 6), then how does Hurley eventually meet up with Jack, after leaving with Locke to go back to the barracks? Any ideas?

Maybe Locke says something about Charlie? Something negative which pushes Hurley away?

Locke did use Charlie to manipulate Hurley into taking his side. Maybe at some point later on Hurley realizes this. It is odd that Hurley apologized for going with Locke.