What do people want in a new iPhone? According to KGI Securities analyst Ming-Chi Kuo, it's OLED displays, an all-glass design, and wireless charging.

In a note to clients, Kuo predicts that the iPhone 8 will kick off an "unprecedented replacement demand" resulting in 120 to 150 million units being shifted during the second half of 2017, beating the approximately 120 million record that the iPhone 6 and iPhone 6 Plus set for the second half of 2015.

Much of this demand, claims Kuo, will be driven by a new high-end iPhone 8 that features a new design, low-energy OLED display, and other "notably superior specifications" that will differentiate it from the "less exciting' 4.7- and 5.5-inch iPhone handsets.

Kuo sees two drivers:

Our rationale is as follows: (1) the OLED model may trigger replacement demand among high-end users given its completely all-new-design form factor and notably superior specs in comparison to the TFT-LCD models; and (2) the new 4.7-inch iPhone, featuring glass casing and wireless charging, looks well positioned to tap replacement demand at the entry level.

But more selling more iPhones doesn't necessarily mean pulling in more profits. Some analysts are becoming increasingly worried that the iPhone is getting more and more expensive for Apple to manufacture, and that gross margins will continue to erode over the coming years. There are also concerns about the availability of OLED displays as well as the fact that the technology could add around $50 to the manufacturing costs.