Okay, so, let's say Jack is successful in getting that bomb to blow up at the Swan.
But here's what I think happens after that, it ONLY succeeds in making the ladder the way we saw it at the end of Season 1 AND it results not only in the release of the electromagnetic energy but it also sends our Losties from 1977 to synch up with those in 2007. And that's the rub, "the incident" was ALWAYS meant to happen, but just like Sayid shooting Ben led him to become what it was, this was always meant to happen and Jack's actions while intending to reverse the crash actually causes it. The cliffhanger? Like others have said, it leaves us wondering if it worked or not and Season 6 finds our Losties back where they started, stuck on the island with some trying to find a way to get off of it again.
But here's what I think happens after that, it ONLY succeeds in making the ladder the way we saw it at the end of Season 1 AND it results not only in the release of the electromagnetic energy but it also sends our Losties from 1977 to synch up with those in 2007. And that's the rub, "the incident" was ALWAYS meant to happen, but just like Sayid shooting Ben led him to become what it was, this was always meant to happen and Jack's actions while intending to reverse the crash actually causes it. The cliffhanger? Like others have said, it leaves us wondering if it worked or not and Season 6 finds our Losties back where they started, stuck on the island with some trying to find a way to get off of it again.