updated 11:36 am EDT, Thu August 15, 2013
Public debut of iOS should happen soon after
A sixth and final beta of iOS 7 will reach developers next week, sources say. The exact day is unknown, although Monday has been a common target in the past. Once testing of beta 6 is complete, Apple is reportedly aiming to seed a gold master internally and to partners on September 5th. Developers will get the code on September 10th, the same day as Apple's rumored iPhone event.
A gold master is essentially the same completed version of a piece of software that will reach the public. Barring any unexpected bugs, that means that iOS 7 will probably go live on iTunes and iCloud in mid-September. New iPhones are widely expected to ship later that month with iOS 7 preloaded.