This discussion is about Cross-Realm Battlegrounds, which Blizzard is adding in patch 1.12.
Cross-Realm Battlegrounds
For the first time in the history of World of Warcraft, you will be able to face off against players from other realms in the Battlegrounds. Coming in patch 1.12 are cross-realm PvP Battlegrounds, linking Alterac Valley, Warsong Gulch, and Arathi Basin so that players from several realms will be combined into one huge matchmaking pool. Replenish your mana, sharpen your blades, and get ready for some brand-new challengers!
~ from the WoW official site.
Pros: Should be a lot less wait time in queues. Meet people from other servers.
Cons: In battlegrounds if your server is new and you are fighting an older server they'll generally have better gear and better enchants.
Do you think this is a good idea?
Sidenote: They also plan to try and increase world pvp.