I think that's why there is the character Ms hawking with Desmond. I believe the future can be changed, but perhaps there are those who don't want it changed. I mean, do we really want to end the show with a main character addicted to drugs and so 'Lost' in life as Jack is, when we've seen him at least try to be everyone's leader. I think that the future will be changed from the one that we have been shown since season 3's finale.