According to Bloomberg (www.bloomberg.com) Apple is ramping up on two bigger-screen iPhones. One model will have a 4.7-inch screen that may be available to ship to retailers around September. A larger 5.5-inch version is also being prepared for manufacturing and may be available at the same time but in smaller quantities.
I have always been doubtful that Apple would release 2 iPhone sizes, but based on the fact that everyone wants a “larger” iPhone, maybe 2 new screen sizes are forthcoming. This is even more likely, as there is always a shortage apparently just before any launch and especially of the version that everyone wants!