Word has it that Apple has planned to ship 80 million units of the iPhone 6 and 6 Plus between the release next week and the end of 2014; and, that should be plenty to meet demand, especially since there were only 60 million iPhone 5s units shipped in the same time frame last year. The trouble is that only 10 million of those are expected to by the end of September. And, that 10 million unit estimate assumes there are no issues with components or production. That might be cutting it a bit close, considering that Apple reportedly sold 9 million iPhones in the first 3 days following the iPhone 5s release.
So, depending on how quickly Apple can get devices to stores, the new iPhones may be a bit tough to come by for a while there. We'd like to give Apple the benefit of the doubt here, because supply chain management is Tim Cook's expertise, but the numbers seem a bit too close for comfort.