"iPhone 6" and "iPhone 6c" concepts by Martin Hajek.
Specifically, support representatives for Deutsche Telekom are said to have been told that Apple's next iPhone will go on sale Sept. 19, according to apfelpage.de. While it's unlikely that Apple has told the carrier or any of its partners about a specific launch date this far in advance, the date is consistent with Apple's recent launches, making it likely an educated guess.
Apple historically launches its new iPhone models on Fridays, and Sept. 19 of this year does fall on that day of the week. In addition, Apple began selling its latest smartphones during the same week last year, as the iPhone 5s and iPhone 5c both became available on Sept. 20.
Similarly, in 2012 Apple made the iPhone 5 available on Sept. 21. Prior to that, the iPhone 4S launched a few weeks later, on Oct. 14, 2011.
If Apple follows its recent release schedule strategy, the company will unveil iOS 8 at its keynote presentation next Monday, while the anticipated "iPhone 6" will be announced in September, about a week and a half before the product will go on sale. Germany is typically among Apple's initial iPhone launch date markets, along with the U.S., Australia, Canada, China, France, Japan, Singapore and the U.K.
Rumors suggest that Apple is actually planning to launch two new, larger iPhone models this year, one with a 4.7-inch display, and a jumbo-sized version with a 5.5-inch screen. The hardware is expected to see a significant redesign, with a thinner frame and a relocation of the lock/wake button to the upper right side of the device.