iPhone 5S can be shipped in limited numbers initially after September 10th launch. A delay in production of next iPhone's fingerprint sensors can limit Apple to ship only 3-4 million units instead of originally planned 10M units.
Apple's next iPhone event is due in another 4 weeks time. September 10th is the date announced to unveil next iPhone also called iPhone 5S, iPhone 5C and probably iPad too. As this date is approaching near, rumor mill is speeding up. A latest of these is come from Digitimes that reports according to industry sources that iPhone 5S shipments "could reach only 3-4 million units in the third quarter of 2013 compared to 10 million units as originally planned due to a delay in production of fingerprint sensors needed for the iPhone 5S."
Taiwan Semiconductor Manufacturing Company (TSMC) has to start the mass production of the fingerprint sensors in May. But it gets late due to an iOS7 integration issue with fingerprint chips. The packaging firm Xintec, a TSMC subsidiary, yields a lower rate that also takes part in delaying fingerprint sensors. Hence a joint team of Apple and TSMC engineers came to help Xintec to speed up the yield rate due to which volume production starts at the end of August.
Third quarter of 2013 will end on September 28th and iPhone 5S launch is expected on September 10. So 3-4 million iPhone 5S units will be enough for 18 days time period. The number of pre-orders or orders can not cause any shortage of the device. And it is also reported that Apple will likely to increase iPhone 5S shipments during 4th quarter as it has more sufficient supplies of fingerprint sensors. 28-30 million iPhone 5S units are expected to be launched during 4Q13.