Last year, Apple simultaneously launched the iPhone 5s and iPhone 5c on Friday, September 20.
Apparently the smaller 4.7-inch iPhone will be called the iPhone 6, while the bigger 5.5-inch "phablet" version of the next-gen "iPhone 6" will be called "iPhone Air." This would surely help differentiate the two devices, however, it appears to be confusing with Apple naming its biggest-ever smartphone after its "Air" products, which are associated with thinness and lightness. If you see the MacBook trend, the Pro models are the bigger, more powerful models, and the Air models are the lightest ones.
Earlier, Japanese daily Nikkei posted two alleged images of the rumoured 4.7-inch iPhone 6 dummy model, side by side with an iPhone 5s. The leaks suggest that the next iPhone will house the power button on the right panel of the device, instead on the top panel seen on current iPhone models.
Apart from a larger display, the iPhone 6 is rumoured to come with a thinner profile, a faster A8 processor, and other new features. The camera of the 5.5-inch iPhone 6 is also said to feature an optical image stabilization system, while the smaller 4.7-inch iPhone will use a new lens module.