The only spoiler in this article is this:
Damon said that we can expect to see another “Purple Sky Event” in the finale, and he used the word “seismic” to describe the finale.
That having been said, here’s my prediction for the finale:
I think Moving the Island will involve using the Orchid to teleport the entire Island through time and space. This will be the “seismic” “Purple Sky Event” refered to in the spoiler.
Furthermore, I think the O6 manage to be free of the effect when this happens, which puts them in the middle of the ocena, free of the Islands forces. They then take the Zodiac to civilisation. The cover story is neccessary due to the total lack of evidence.
The Flashfoward in “The Shape of Things to Come” implies that Ben teleported from the Orchid to 2005 Tunisia. I think he left Locke in charge of the Island and is now on his own little mission of revenge against Widmore. His confidence that Widmore will never find the Island suggests it has been teleported and thus whatever information Widmore had that helped him find it is now useless.