The factions can and SHOULD remain they are integral to the story WoW likes to tell. However the faction restrictions splitting the player base must go for the health of the game. All players should be considered adventuring Mercenaries who can group with who we like. The cities do not have to tolerate opposing factions so you wont see gnomes in Org or orcs in Stormwind. But I should be able to invite my friends who picked a troll because they liked them while playing my night elf because I liked them.