According to a GamesBeat source 70 staff on Blizzard's upcoming Titan project have been reassigned leaving a core team of around 30 to restart production on the game which will now not be released until 2016 at the earliest.
Titan, a codename for the project, was first reported on in 2010 and it was expected to launch either this year or in 2014. The delay comes amid declining subscriptions for World of Warcraft which lost 1.3 million players in the first quarter of 2013.
Blizzard, not known for speedy development times, has issued GamesBeat with a statement commenting "We've always had a highly iterative development process, and the unannounced MMO is no exception. We've come to a point where we need to make some large design and technology changes to the game. We're using this opportunity to shift some of our resources to assist with other projects while the core team adapts our technology anf tools to accommodate these new changes. Note that we haven't announced any dates for the MMO."
Based on what Blizzard has said it certainly seems that GamesBeat's source was correct.
While it might be some time before we see Titan, or whatever it's ultimately called, Blizzard plan to release Diablo III on PS3 and PS4 while they're also developing Hearthstone, a World of Warcraft inspired free-to-play card game, and you can currently sign up to the title's beta.