I picture it as Sam still being the psychic one and leaving to go off to college. I see it as Sam still having fought John on hunting and additionally resents John for leaving him to take care of Dean. Dean's personality is the same too and as a kid tries to do things on his own so as to burden his big brother, but as a 14 year old, when Sam leaves for college he feels like it's his fault b/c Sam had to take care of him.

I should probably write this, since I *obviously* have thought about this a lot. Hee

You're more than welcome to give it a try if you want, I'd definitely read it.