I think there are 2 scenarios that could play out: (1) we are just watching what always happened....this is the incident as it has been previously alluded to throughout the show....basically the "past" or rather the time period between 1977 - 2007 does not change OR (2) we just watched something different...which will/could lead to a change in events from 1977 forward with alternate timelines/events.
I think (2) is entirely too messy. You'd get into all the changed events being the sole focus not the characters. It would cause too many questions to be asked and too little time to answer them (not that every question has to be answered, but some fundamental "truths" would have to be in order to provide some focus to the show).
Scenario (1) would effectively provide the writers more ability to focus on character development/resolution while at the same time providing mystery/suspense/drama. They could easily transport (due to the bomb detonating and the losties being catapulted through time due to the energy release) to 2007 where they meet up with everyone and then work towards their own final destiny. That storyline still provides mystery and intrigue (who is Mr. X, who is really "good" and "bad", etc.), but wouldn't have to focus on time travel quantum physics, alternate timelines, etc.
I suppose they could possilbe use a variance of both (1) and (2), similar to what Desmond experienced. That would be, imo, the absolute most difficult thing to accomplish for the writers. Essentially, those Losties near the incident would be able to mentally travel "back" in time (at least in their personal expereince of time) to 2004 right before/after the plane crash. They would all be their own "constants". The ending scene of the finale (which was the opening scene of season 1 episode 1 where jack wakes up in a jungle after the crash) coupled with the change in how the LOST showed up on the screen (it was always white letters with a black background, now it was for the first time black letters with a white background) kind of seem to indicate a they might go that direction.
p.s. I think about this way too much.
