Source: http://www.ign.com/articles/2013/11/...in-development
In an interview with Polygon, studio co-founder and president Mike Morhaime explained the developer was trying to pick up the pace at which it releases fresh content for the ageing MMO.
I REALLY hope this not turning in the Everquest II model with every year one new Xpack that got little to no content after Warlords of Draenor"It's going to be on us and our development team to continually look at ways to evolve the game and keep it relevant," Morhaime said, "and look for new ways of maintaining engagement within the game. We view expansions as a huge opportunity to do that.
"We recognize that we need to release them on a faster cadence than we have in the past. So we're investing in the team and our resources to enable us to do that.
We also have to start looking further down the road and planning further out. We've already started working on the expansion after this one [Warlords of Draenor]. We've never done that in the past. We've been doing one expansion at a time, sort of a very linear content creation model, and we've looked at ways that we can parallelize that. So that while we're working on this expansion we're looking at the new one."