Fact one if Kelvin comes to the island and he wasnt on the island when the bomb went off wouldn't that some how undo some part of the island history to the ones in 2008? well no the only person to come in contact with him is in 1977 so it wont have any effct to the time line. Fact two what will happen if the people in 1977 go to 2004 we will still have the people in 2008, what are they trying to fix? are they moving the island in time by stoping the hatch or are they changing the time line of there lives. Not so fact but just i dont know what to call it, but with the island, even if all this happens how will this work on Des and the rest of the people off the island in 2008. Fact 3 didnt jack set the event's in place already? after all he did tell Richard not to give up on locke and we have seen what happens there and if it isn't for Oceanic Flight 815 how will john get on the island.