Preview at WWDC likely in June, followed by September launch.
Report Claims Apple Will Launch 4.7-Inch iPhone 6 in August, Larger Model in September
An August launch of the iPhone 6 would be a different strategy for Apple, as the company has launched the past three versions of the iPhone in September or October. The news also contrasts prior reports claiming that the 4.7-inch iPhone 6 will launch in September, with the 5.5-inch version not launching until later this year or early 2015 due to issues with the device's battery life and display technology.
In addition to a larger screen, Apple's next-generation iPhone is expected to include a thinner profile, a faster A8 processor, and an improved camera. Jefferies analyst Peter Misek also claimed last month that Apple is negotiating with carriers to raise the price of the iPhone 6 by $100.