World pvp... Yay.
I personally love open world, no toggle, free for all pvp but I'm in the minority here and I know this.
Many more prefer pve content (questing, grinding, crafting, etc) Where one can play in a controlled environment; Enjoy the sights, socialize with their friends (or relax alone). Just play without being bothered by the adrenaline junkies.
I used to love playing old full loot pvp mmos like Shadowbane and Darkfall for example. Many pve people who tried these two games left the game real fast never to return. So they became small niche mmos.
If you want people to linger and not quit your game, make regions where people can quest and such without their nerves being shot because they got killed. Would be fun to have an area out in the open world to do pvp as well.
I do think though, I don't know if this is even possible to do but... If a low level player is killed by a high level or a solo player is ganked by plus 3 players. The dead player will neither give the higher/gank squad any xp or loot :P