I always thought that when she grows up she'll certainly be perverted, but with a better than 50% chance of turning into a rather creative dominatrix. If she does go the other way then I figure she'll be more of a bottom than a sub, yelling, "Whip me harder you momma's boy or I swear I'll tear your nipples off."
Harry and Ron will obviously fall for each other, and have more than a bit of fun with Hagrid's enchanted gerbels.
McGonagal and Snape are obviously both switches, and probably spend a lot of time in the dungeons teaching each other new perversions.
Dumbledore is a top, no question.
Poor Voldemort is just a misguided sub looking for the right Mistress or Master to keep him in line.