I for one cannot handle another ride through space unless they somehow end in 2007/2008 whichever!!!The eye at the end bugs me. Makes me think that they did not stop anything! They are still on that island...they just flashed to that time period because that's what Jacob meant by "they are coming".
If the bomb exploded: it destroyed the swan, killing everyone in range, not just Juliet!! The young Jack, and so on grow up off island and maybe still come back because Jacob did touch them all and it is their destiny to be on that island! And if they didn't where is the fun in that???? Our losties grow up to live their lives...no no no don't think so Jack!!
If the bomb exploded: and nothing changed, they caused the incident then what a wicked time loop they would be in!!! The young Jack and Kate and whoever else are not gonna know, hey maybe we shouldn't get on this plane today!! So who is to say they wouldn't do the same thing!!
The island may have its own way of course-correcting. I think it was a flash of some sort hopefully to the same time period as everyone else, then that would mean: Juliet is laying at the bottom of that huge crater (because the hatch was destroyed and all that was left was a huge crater) and all the others are where they were when we last seen them....Jack is probably the eye we seen at the end of season finale. oh well I guess we will have to wait until JANUARY to find out!!!