Mike Morhaime, President and Co-Founder of Blizzard said to Polygon in a interview it's been cancelled and why it has.
He said
"We had created World of Warcraft, and we felt really confident that we know how to make MMOs"
"So we set out to make the most ambitious thing that you could possibly imagine. And it didn't come together."
"We didn't find the fun, we didn't find the passion. We talked about how we put it through a reevaluation period, and actually, what we reevaluated is whether that's the game we really wanted to be making. The answer is no."