"We appreciate that our players want the story to continue to expand, and it will, but we do not release our timeline or our plans. You'll know more about what's coming in the Spiral when the Test Realm opens later this year."
Doesn't look like the new world is coming out anytime soon, so my guess is that we might test this upcoming content this Fall (either November or December), considering October will be a busy month in the Spiral with the Halloween events and new quest.
What do you think will happen? Will the new world come SOONER or LATER? What will be the theme? So many questions to ask.