Honey, I think it's too late.

We already have each boy representing a side of the battle between good and evil.

Funnily, ha ha, the "good" boy (Sam) represents evil, and the "naughty" boy (Dean) represents goodness. BUT. At the same time the "naughty-but-good" boy is the one who spent 10 years torturing people.

In the end, however, I think both boys will rejoin with their humanity and go back on the road again.