Can the future really be significantly changed? I don't know - well, like Claire said in S1, The future isn't written in stone. But somehow, these changes seem very peripheral.

F!Peter tried to stop Nathan by shooting him; in the end, Nathan still ended up betraying his own kind (well I guess we need to watch V4 to fully establish this, but it certainly looks like it for now). This also seems to match up with the future portrayed in S1's FYG - where Sylar tells Peter: Your brother turned against his own kind, before I did or something to that extent.

If the future cannot really be changed, then it's also in tandem with what Hiro said in S1 (when he tried to save Charlie).

Sure, changes occur - in Hiro's case, he managed to take a picture with Charlie & learn quite a lot from her, in S3's case, Peter & company certainly went one long way to prevent the Heroes from facing doomsday - yet the fate that eventually arose seemed no different from when they first started out.

Any thoughts?