Would you like more content like Isle of Quel Danas? Where the collective effort of players has impact and change the world? Maybe they can do it all over the world.
There will be multiple progress like in Isle of Quel'danas and maybe this time the impact could be reversed if the players lose or not do the quest anymore. So doing the quest remains having an impact even if players reach max progress. Maybe it gets even harder at max progress. Max/higher objective would be world bosses or outdoor dungeons. Wiping/dying on monsters helps reverse the progress.
Then there would be reward along with the world change too. Like buffs, daily trickle of gold and profession mats. Along with new quest. Losing progress made will take away their rewards.