Pretty much every story must have a protagonist and an antagonist, and this game is no different. However, in the good guy always wins story arc the protagonist is supposed to beat his opponent. I see these battle lines being drawn as the "good guy" alliance and the "bad guy" horde. So if blizzard adheres to the accepted format the horde should lose because they are the "bad guys," but is that really fair? Or should we just accept the likelihood that the hero will triumph over evil.
I know perspective might suggest the alliance are bad, horde are good depending on which side you play but in reality the monsters are the horde and the good guy humans are the alliance.