http://pc.ign.com/articles/718/718310p1.html
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the new world PvP content will take place in Silithus and Eastern Plaguelands, although it may eventually branch out to other areas. Silithus and EPL are the highest-level zones in the game right now anyway (Deadwind Pass is too small to count, really), so it will generally be level 55-60 players bashing away at each other.
In Silithus, the objective revolves around collecting dust, called "silithyst," and players will activate the geysers to collect the silithysts. You get a nice "buff" (stat boost) when you turn in the resources, but you'll be flagged as a PvP player as soon as you pick the stuff up, making you attackable by anyone in the opposing faction while you attempt to make your way back the Field Duty camps associated with the Cenarion Hold faction quests. If you manage to turn in enough of the dust, all of your fellow faction members in the zone will gain a buff as well, including those in the "AQ20" Ahn'Qiraj dungeon. Also, Blizzard tells us that no new PvP rewards are on the horizon, although faction and PvP honor points will be involved.
In the Eastern Plaguelands, we'll have a PvP mode that's similar to the Arathi Basin play style, rather than the resource collection in Silithus. There are several towers in this zone, already standing, that will be converted to captureable bases. You'll need to control and defend each tower, and the faction who possesses all four will gain zone-wide benefits like in Silithus. In addition to increased damage against the many undead creatures there (and in Stratholme), there will also be PvP-specific flight paths connecting the towers to each other. Although this game type has been prone in the past to tactical exploitation by rogues and other stealthy classes, Blizzard plans to implement a feature where the time it takes to capture a tower is reduced according to how many friendly players are nearby. If you are a stun-kill-disappear commando, you may find your usual tactics less useful here. Also, unlike Silithus, there is no automatic PvP flagging.