The war between the Alliance and Horde is central to World of Warcraft. However, this war will get more complicated with the future introduction of a new Mercenary mode that lets players turn on their own faction.
Once this feature is live, players will be able to act as a mercenary for the opposite faction in PvP activities:
Whenever your faction is experiencing a long wait time to get into Ashran or unrated Battlegrounds, agents of the enemy faction will appear in your base in Ashran (Stormshield for the Alliance, Warspear for the Horde). These agents will allow you to enter Ashran or Battlegrounds disguised as an enemy player, and actually fight as the opposite faction.
There are a few benefits to this Mercenary mode. For starters, it should reduce queue times for players looking to jump into player-versus player. Your character will morph into a race from the other faction so it's a chance to have a very different appearance and set of racial abilities, if only temporarily. On top of all that, you'll still earn the usual PvP rewards aside from faction-specific achievements.
Blizzard reiterated in a follow-up post that this mode will only be available when a faction is experiencing very long queues thanks to an imbalance between the two sides. They also said that they're trying to make the feature as unobtrusive as possible:
Using the Mercenary Mode system is completely opt-in. It's important to us that if you don't choose to participate in Mercenary Mode, it doesn't affect you. Should you be grouped with players who are using the system, they will not be identified to you as mercenaries -- they'll look like just another player from your faction.
Players currently seeking faster queues for PvP can spend cash on permanently changing their character's faction or server. This approach has drawbacks besides the cost, though. Transferring means that players can potentially be separated from friends - which is bound to hurt their enjoyment of the game. Mercenary mode seems like a much cleaner way to allow players to experience player-versus-player in a timely manner.
Over World of Warcraft's ten years, Blizzard has added several features to account for low or imbalanced player populations across the game's servers. Players from different servers can now be matched up automatically for dungeons, raids and battlegrounds. The developers have also linked questing zones and auction houses across servers as well.
WoW's population has tapered off as it ages, with especially large dips in the last months of a given expansion pack. These features, which allow players to easily find others to enjoy group content with, are essential during these periods. If players can't play the MMO as intended, they're not going stay paying subscribers for much longer.