In the opening keynote for WWDC 2012, Apple confirmed that OS X Mountain Lion will hit the Mac App Store in July for $ 20 β for both Lion users and those still on Snow Leopard. But July, of course, is still somewhat comprehensive.

With the launch approaching, Apple has already extended testing of its new operating system to Retail Store employees and recently released a new build internal for developers β possibly the last before the release Golden Master (GM).
Just now, the MacRumors said Apple announced a freeze freeze for July 22-29, in preparation for something not yet announced. This can have a lot to do with the availability of Mountain Lion, of course, but it can also indicate the arrival of updated Macs. Last year, on the same day that OS X Lion landed on the Mac App Store, Apple updated MacBooks Air and Macs mini β in addition to launching the Thunderbolt Display and killing the old white, polycarbonate MacBooks once and for all.
A few days ago, the site T-GAAP he said he heard from a source that the Mountain Lion would be released on July 19. Thursdays, however, are not usually days of big Apple releases like these. It would make more sense on a Tuesday or Wednesday β 17th or 18th of July, if we are optimistic, or even more likely 24 or 25 (in the middle of such a freeze).