So I thought that was a great episode- apart from Juliet dying. I just can't get behind that; probably because I hate Kate, but whatevs.
Joe mentioned the parallel realities intersecting in his earlier post, and I thought I'd share a thought one of my friends from school had. He thinks that the flash-sideways is actually a flashback to the past that ultimately didn't change anything. While there have been differences in the sideways timeline, they generally tend to be small (Jack being the nervous flier-not Rose, getting one bottle of vodka- not 2, etc.), and there seems to be a lot of course correcting going on. The details may be different, but many of the overarching plot points are the same. Charlie almost dies and Jack saves him. Boone tells Locke that he would follow him anywhere. The Marshal is injured (he'll probably die later), and Kate escapes. I would be willing to bet that Locke will walk again at some point (thought with Jack's help as opposed to the island's), Kate and Sawyer will have sex, and Kate will end up with Aaron. Anyway, he thinks that many (if not basically all) of the major events from the past five seasons will still happen; it will just be off the island. At some point, the convergence of the timelines will come when they eventually end up back at the island. After all, the Lost mythology generally states that you can't avoid fate. Charlie tried, with Desmond's help, and failed, and Desmond himself got a similar lesson from Eloise Hawking in an earlier season.
Having said all that, one of the major flaws in this theory is that we saw the island underwater at the beginning of the episode. So I don't know. On the other hand, that could have only been a part of the island, or only one of the islands, and really, I wouldn't put it past them to somehow "resurrect" the island. Most things aren't too far outside of the realm of possibility in Lost anyway.
