Rumors exist that Apple is preparing to increase the display area of the iPhone. People familiar with the company have cited that apple is looking to contract with Sharp, LG and Japan Display to build screens for the device.
Multiple manufacturers may be used to increase the speed of production. One reason iPhone rumors about a 4-inch screen exist is because of the increased size of Android-based phones that are from manufacturers such as Samsung. Another reason for the size increase for the iPhone is the size of the current screen has reached its display limit.
Increasing the size of the display also will increase the size of the casing. The increase of the casing can be a sign that Apple is upgrading the device for 4G. A bigger battery may also be necessary to provide a phone with increase power that is needed when using a 4G LTE network.