I saw it as more a comment on Elizabeth than on Jack. No I don't think he'd have jumped ship, but I think it was important to Elizabeth's character development that she was prepared to do it. what I want to know is

would she have kissed him anyway? or was that just entrapment.

and the state of her in Tia Dalma's hut - did she really regret it, or was she upset in a "that needed to be done" kind of way?