Although related to Guild Wars 1 story-wise and set in the same world in the distant future, Guild Wars 2 is a completely different game from its predecessor. The world is not instanced and everyone shares the same open world and town. Done away are the "holy-trinity" of classes and everyone is responsible for themselves. Only a one-time fee to purchase the game and there are no monthly fees.
http://wiki.guildwars.com/wiki/Guild_Wars_2
Release Date: August 28th, 2012
I currently have it on pre-order and the game absolutely looks amazing.