According to Digitimes, there will be two separate iPhones planned for 2013, but both featuring a 4-inch display.
Recently it was reported that Apple plans to introduce a low-cost version of the device with a larger screen in 2013.
But sources cited by the Taiwanese site indicate that while Apple is indeed working on an iPhone with a larger display, this year such a device will not be launched.
Instead, in 2013 two Apple smartphones, will be released, one of which will be designed for China and other emerging markets.
The insiders also say that it is not clear whether there will be enough in-cell screens available for the new iPhones.
Meanwhile, the iPhone supply is projected to reach about 37 million units in the first quarter of 2013, with 20 million of them being the iPhone 5.
In the second quarter, shipments of iPhone 5 will decrease further to around 18 million units.