Apple's yearly developer conference should see iOS 8, OS X 10.10, and likely some hardware.
T-Mobile Employee Blackout Dates Support September 20 iPhone Release Date
During the blackout period, employees will be unable to take vacation time to ensure that T-Mobile has adequate staff on hand for a large release event. Similar blackouts have been instituted for the launch of previous iPhone models and other high-profile products.
While MacRumors has heard reports of a September 20 blackout date for T-Mobile employees, reports from AT&T and Verizon employees have been conflicting, with some citing an October blackout period. Blackout dates are occasionally instituted for a broad range of dates and then narrowed down as a release date approaches and can also be subject to change based on Apple's exact event plans.
Apple's iPhone 5S and iPhone 5C are both expected to be revealed at a September 10 event that has been confirmed by multiple sources, which makes September 20 a likely candidate for release as Apple typically launches its new phones in the United States and other markets approximately a week and a half after they are announced.
Last year, Apple announced the iPhone 5 at a media event on September 12, launching the phone several days later on September 21 in the U.S., Australia, Canada, France, Germany, Hong Kong, Japan, Singapore, and the United Kingdom.