i'm going to spoil all of this, i dont think it was a flash forward, i think its like what desmond had, but he CAN change it
so call it a possible path for jack... and only locke knows these possilbe paths, thats why he said ' your not suppose to do this ' just a thought eh?

and why would jack be upset that walt died? they didnt talk, and also if it was walk would his dad be there? micheal and his mum... we can rule out walt... i dont think its sawyer..