We’re going from late to early summer, which is not bad at all. However, there is something that will be delayed until autumn in OS X Mountain Lion: the integration with Facebook .
Presumably this integration will come with a system upgrade. And the reasons must be purely based on deals with the social network, because it looks like the Facebook integration will come out at the same time in OS X as in iOS, with the iOS 6 update that is supposed to come out this fall.
For the moment, and if you have an Apple developer account, you can test and give feedback about the integration of Facebook in the new fourth draft version of OS X Mountain Lion that the company has launched to show all the new features revealed in WWDC 2012. As soon as the system is launched on the Mac App Store, this integration will disappear until autumn.