I see this happening during the game. It could be especially cool given the "no camera cuts" thing they are going for. Something like BIG DRAMATIC SCENE KRATOS DIES OH NO! zoom in on the kids eye, zoom out and he's now an adult
All I can think of is that Arrested Development where they had the Banana stand war with Michael/George Michael and Gob/Steve Holt and George Michael starts to tell them the recipe for the frozen Banana.
George Michael:"Well you just take a banana and stick it the..."
Michael: "No no don't tell them that."
Steve Holt: "Stick it in the What? STICK IT IN THE WHAT???!"
I don't think he will die in the opening. In my opinion, he will die at the end and the ending is gonna be all about his son being the new protagonist.
I agree that the exp points are gained for the boy, but I believe this will be a mechanic of the whole game, not just of the beggining of it.