See, that's the thing that is confusing me. I feel like the Island did "move" somewhere in space and time... but the people on it (Sawyer, Juliet, Locke, Faraday, etc.) are the ones that are skipping around in time. So what happens when the O6 go back? Do they go to the "real" present-day Island? Or do they go back to the time/place that the Leftbehinders are skipping around in?
Yeah, I'm feeling there is a 70-hour window when the Island will be in 2008. Ben has to gather all of the O6 + Locke's body and get them back to the Island inside this window because the Island won't be in a window in which they're alive ever again. They all get back onto the Island in 2008, but it skips back to a hugely distant past before they can anchor the Island (and the on-Island Losties) in time. I love the idea of a 4-toed Sawyer ruling over ancient flaming-arrow-shooters, whom they will revere as a god because of his advanced knowledge compared to their primitive ways. I also think that Locke telling Jack that they were not ever supposed to leave the Island is because that's where they all died after the Island was anchored in the ancient past. That would allow Locke to "become" Jacob. Getting everybody back to the Island before it gets re-anchored appears to be the ultimate course-correction that is needed, otherwise "God help us all".