Blizzard announced today several changes to the PvP system coming up in the next big patch. Below is the announcement, and for a lot of additional information follow the link to the PvP info page.

Player-versus-Player Gameplay News
Many of you have been eagerly awaiting news of the player-versus-player gameplay in World of Warcraft. We have maintained from the beginning that the current rules as they stand are temporary and that the real PvP system has yet to be added. Beginning with this upcoming patch, we will be introducing some elements of our final PvP system, and we will continue to flesh it out in successive patches after this one. But we also wanted to relate to you our philosophy behind our PvP system, reveal some concept art for our battlegrounds, and give you a sneak peek of where we are ultimately heading with World of Warcraft's PvP gameplay. Check it out here.