It hasnt. You could watch an episode now and you havent missed anything so you'd soon pick it up from the most recent show. They are still Lost and wierd unexplainable things still happen with no answers. It will still go on like that for many series yet, I'm sure. Will any of the unexplained stuff ever get answered....? I doubt it, the show isnt about explaining the unexplained, its about everything that happens in the world that makes you go 'umm thats strange....' but there will never be answers or progress......it sounds like its made no progress what so ever since season 1.