Last we heard of the MMO Titan, the project had reportedly been pushed back to 2016 and some of its staff shuffled around. During a quarterly earnings call for Activision Blizzard, it was clarified by Blizzard CEO Mike Morhaime that the company is "in the process of selecting a new direction for the project and re-envisioning what we want the game to be."
That would explain why we've only heard rumblings about this thing despite it being in development for what feels like quite a long time, at this point. It was, what, 2007 when word of Titan first broke? Morhaime did give one additional tidbit during the call: "While we can't talk about the details yet, it is unlikely to be a subscription-based MMORPG."
I don't know of anyone who enjoys paying monthly fees, so that's nice to hear.