The multiworld suggestion has so far received unanimous support.
Offical vote, majority of vote will get their way.
To reiterate:
The world boundary is removed
A 4th world (a pvp world with a 1k boundary that gets reset everytime terrain generation is updated) is added. People can tp between them freely (they have to wait for a certain amount of time to prevent it being used as a combatlogger) your location in each world will be saved. So say you're at x:10000 y: 8 z: 40000 in the main (normal) world. You've never been to the pvp world, so you get teleported to x:0 y:64 z:0 in the pvp world. You then walk to x:500 y:80 z:300 in the pvp world, and then decide to teleport back to the normal world. This takes you back to x:10000 y:8 z:40000. After getting some more equipment, you teleport back and end up at x:500 y:80 z:300.
Wait, that could be majorly abused. If you're in your base, chilling, and you tp to the other world, and someone else is up ground, traveling, they would see, and assume your base is somewhere below them. Hrm.