Public launch September 17 ahead of iPhone 6 debut.
Apple Planning to Wipe CloudKit Data for iOS 8 and Yosemite on July 7 Ahead of Beta Updates
The wipe comes just a day ahead of the rumored launch date of iOS 8 beta 3 and also the likely launch date of the third Yosemite Developer Preview. Apple commonly seeds early versions of its iOS beta operating systems on roughly two-week intervals, moving on to three-week intervals later in the testing period. OS X beta updates have followed a similar update pattern in the past as well.
Apple's second iOS 8 and Yosemite betas came approximately two weeks after the software was first provided to developers at the Worldwide Developers Conference, and it has now been three weeks since those updates were seeded.
Both iOS 8 and OS X Yosemite are expected to be released to the public in the fall, after an extended beta testing period.