That can do anything in Lost of course but the way I see it is, with the season just gone they have pretty much covered all of the backstory which has been mentioned in previous series, i.e. the origin of the Dharma Initiative and the hatches, how the others took over, what Ben has been up to and what motivated him, probably where Richard came from (Black Rock is my theory), and the time travel ability of the island. The only things which are proper unexplained is the statue and the thing with children on the island, though on some of the Lost sites they have linked those together as the statue is very similar to some real life statue to do with a pagan god of motherhood or something. This along with Jacobs "They're coming" statement suggest to me that the next and final season with have no "backstory" or "how did we get here" type elements as such, whoever "they" are will turn up and it will end up being a basic save the world scenario. I am just hoping it is not something as derivative as aliens. I could deal with something religious, like gods or something, as long as its not aliens.
edit: Oh, and my prediction for what effect the bomb will have had for the beginning of next season is that it won't have reset them back to everything before they even got on the plane, I think it will simply jump Kate, Jack, Sayid etc 30 years into the future so that they are on the island in the same timeframe as Locke and the rest. This would negate the need for any time consuming efforts to get back to the island again, as I'm sure they would be driven to do by some revelation. Alternatively they could reset back to the time before they got on the plane, but would retain all their memories of the time spent on the island, and again by some revelation they all have to get back to the island again. Depends how many episodes they want to take up before the final proper explanations begin.