We've received no official announcement, but several reports have rolled in that the three day Guild Wars World Preview Event slated for this weekend is now underway. Here's a bit on what's going on:

ArenaNet and NCsoft are proud to announce the second Guild Wars World Preview Event! During the last three days of October, players from around the world are invited to play Guild Wars and enjoy a completely new Guild Wars experience. The World Preview Event offers two new regions, new cooperative quests, a new strategic battlefield for arena combat, new items and monsters, and the ability to level-up your character. And for the first time you can start forming guilds, experiencing guild warfare, and building your guild rank.