Blizzard has said with Mists of Pandaria, it plans to add more PvP content "than we’ve ever had before."
According to the firm, this constitutes two new Battlegrounds with new gameplay types, and a new Arena bringing the count of Battlegrounds up to 10 and the Arena count to six.
"We’re very deliberately trying to get people back out into the world, and so that means on a PvP realm, you’ll have more people to kill that are out in the world," said Tom Chilton. " [But] there are no plans to force PvP on players who are on PvE realms. Their experience shouldn’t change and they’ll have the same opportunities for PvP as they do now.
"It’s also worth noting that the Black Market Auction House has the potential to become a world PvP location for those on PvP realms. They are not in neutral or safe zones. For PvE realms, it’s not going to have that same risk for placing a bid as on a PvP realm."
Chilton also said the team plans to adjust the guards which bar entry into some of the towns, but only on PvP realms to where they aren’t quite as strong as on a PvE realm. They won’t respawn quite as quickly either, but on PvE realms, the guards will remain the same as they are now.
As far as the number of players available to participate in large scale PvP, Chilton said the introduction of Cross-Realm Zones tech should help make sure more world PvP happens.
Another change is the restricting of flying mounts within Mists of Pandaria to level 90, and there's an item being added to the game players can use from the ground so it's possible to dismount a flying enemy player. He wouldn't go into further detail on what this item was as the teams is still working out the specifics.
You can find out more regarding changes and additions coming to PVP with Mists of Panderia over on Battle.net.