As pointed out a new PvP world would be fun and used for a week, maybe a month at best then few would bother to go there. One of the prevailing issues is the gap in gear between someone just getting started out and a player who has pimped out all of the best gear. That in mind what is to keep most players coming back once they have their PvP rewards/gear from that planet?
WoW had an interesting partial solution to this by combining PvP with unlocking PvE raids (Winter Grasp and Baradin's Hold). Maybe something similar could be introduced to entice more players to go to a PvP world than would normally.
Since PvP in MMO's has been notoriously unballanced I tend to avoid PvP for that reason. However when provided with something I do want (a PvE raid my guild wishes to run for example) I will jump in to try and help my side win.
Other things WoW used to try and entice player into PvP were PvP faction specific gear, mounts, pets, tabards and achievements (yes some of us wasted months of our lives earning as many of these as we could). My point is any PvP specific area will need something to lure players into coming back after the initial fad of the new area wears off.