Blizzard announced information regarding the PvP Battlegrounds today:

PvP Battlegrounds Preview - Part 1
One of the core tenets of the Warcraft universe is the raging conflict between the Horde and the Alliance. Old hatreds die hard, as they say, and the hate shared between these two ancient foes is deep and primal. That's why the player-versus-player gameplay has always been a staple of the design for World of Warcraft; the war between the Horde and the Alliance simply isn't over. It might not look this way now, because our full player-versus-player system isn't in the game yet, but the introduction of Battlegrounds, and the full PvP reward system, will change that perception. We've been testing Battlegrounds and our reward system for weeks internally now, and we're ready to bring you a full-blown, multi-part preview of what we have in store for you in the months ahead. Click here to read more about the upcoming PvP Battlegrounds.