Apple estimates that demand for the iPhone 6 in 2014 will be around 60 million units while demand for the iPhone 6 Plus will be around 15 million, according to sources from the upstream supply chain, who added that the iPhone 6 and 6 Plus may also suffer from iPhone 5S and 5C's dilemma, whereby the iPhone 5S took most of the demand, leaving the 5C to suffer from inventory issues.

Although some component makers believe the iPhone 6's 4.7-inch display is sufficient for most consumers and demand for the smartphone is expected to be much stronger than that for the iPhone 6. Plus, some makers believe the iPhone 6 Plus' 5.5-inch display and longer battery life should attract more demand and the price gap of US$100 will only have a limited impact on demand for the iPhone 6 Plus.

Demand for the iPhone 6 and 6 Plus will also affect Apple's orders to its upstream manufacturing partners. Orders for the 4.7-inch iPhone 6 are currently being shared by Foxconn Electronics (Hon Hai Precision Industry) and Pegatron Technology, while the 5.5-inch iPhone 6 Plus is solely supplied by Foxconn.