Just wanted to add my voice to those that would love to see the return of both of the lost continents at some point – Cantha as well as Elona. Such and extraordinary amount of lore and culture there, it would be a terrible shame to never revisit those locales.
But furthermore, Cantha and Elona brought something to the original Guild Wars that you rarely find in MMO’s these days – diversity. So absolutely, please bring back these lands in expansions to come!