There is nothing official yet. As you can see, the WWDC site is still caught back in 2012.
Don't be so glad about yearly upgrades of Mac OS X, Apple seems to have it ****ed up in some ways with Mac OS X 10.7 Lion and wanted to paint over it with a newer shiny version of OS X 10.8 Mountain Lion. An upgrade every two years seemed to have fared quite well with Mac OS X before since Mac OS X 10.3 Panther at least, but I guess Apple wants to keep up and go ahead with its OS X version like it does with its iOS version.
But then again, I am not a proponent of Apple's current Mac OS X strategy and am still using the Windows XP of Mac OS X, Mac OS X 10.6 Snow Leopard.