ok ive been racking my brains tryin ta think of a theory,and to be honest most of you guys here seem to have most of the theories nailed so i wont try to come up with a complete theory (im not that clever)i will say this if the time theory and making good on past mistakes theory and destiny life chose theories are correct,with the flash forward now in place....maybe just maybe whatever happens between now and the very last seconds of the very last episodes,maybe the last scene will be jacob (or the island or some other entity we have`nt met yet)apearing before jack.jack finding out that it all went wrong and the only way to fix everything is for him to give everything up including his life now to go back to the very beginning of the show,remember jack woke up lying on his back in the middle of the jungle,i dont know about you but i always found that strange i mean he had to run to the beach.he just seemed to far away and just lying there on his back.so there you go i dont know if it holds any water at all but it is an idea