Is Blizzard working on a fifth game?

Around the time World of WarCraft: Cataclysm was released, a supposed leak reached eager ears.  A Chinese manager in Blizzard's Chinese holdings leaked this image:

In it, you can see StarCraft 2: Wings of Liberty launched in the window indicated on the image.  As did Cataclysm.  Diablo 3 and StarCraft 2: Heart of the Swarm were rumored to be launching near the end of the year, though it is thought now that they will not launch til 2012.  Blizzard said that if they could not get one game out in 2011, they would release two in 2012 [Rock, Paper Shotgun].

See how the StarCraft 2, Diablo 3 and WoW expansions are all fairly evenly spaced?  If you check the release dates for WoW and it's first three expansions (November 2004, January 2007, November 2008 and December 2010), you'd see that the quarters indicated aren't unreasonable.

Note now the game at the bottom.  Titan.  Listed way out in 2013.  It was confirmed [Massively] in December 2010, though of course it's actual release date is unknown.  WoW was announced in 2001 and released about 3 years later, so Titan fits that schedule.  People might argue that if indeed Blizzard has 5 games on the go, they might not make such an early release date, seeing as StarCraft 2 and Diablo 3 have been a decade in the making.  However, WoW had made them a lot of money, and continues to be a fantastic revenue stream (12 million subscribers at 15 dollars a month... do the math).  They should be able to afford a number of design teams, and able to work on multiple games at the same time, sharing experience and knowledge as necessary.

So, we've got a graph that shows a few already released games meeting the deadlines outlined.  It correctly names Titan as their next game.  It shows StarCraft 2: Heart of the Swarm and Diablo 3 as releasing last quarter of this year, which could have been on the mark at the time the graph was released.  It feels legit.

And now onto the meat of my post.  A job posting spotted by eagle-eyed Blizzard fanbois lead to speculation that Blizzard is working on a fifth game [Kotaku].  And I believe it's another MMO.

Early this year a fan made mod for StarCraft 2 got people excited: World of StarCraft.  Which was very quickly hit with a cease and desist [Neoseeker] order.  Many companies do this just to protect their brand names and trademarks, and to allow them the possibility of creating their own.  Blizzard may have simply been defending it's trademark.  Or it could be that Blizzard is planning or working on a World of StarCraft already.

Check out this interview given by Frank Pearce to Arti Gupta of IT Business Net.  In the closing comments of the interview:

A.G.: What can you tell us about other games you have in development?

F.P.: Um…nothing? Laughs

A.G.: I was afraid you were going to say that!

F.P.: It’s no secret that we’re working on an unannounced MMO, but we’re not talking about it.

Is it possible that the fifth game is another MMO, possible based on the StarCraft background and storyline? I know that they have not technically announced Titan, but they did confirm it's existence.  The "Unannounced  Game Title" section on Blizzard's job boards has apparently vanished, and links pointing to it show up as blank pages.