ET News suggests Apple will adopt OLED panels for all three 2019 iPhones.
The South Korean news site would have spoken with Apple officials:
"Apple recently started planning the iPhone model in 2019 and decided to adopt OLED in all three types," said an official from Apple who said, "The OLED used in the iPhone X (TEN) is a low temperature polysilicon (LTPS) LCD Quality, performance, and so on. "
Another official said: "Apple has decided to put all the OLED on the new iPhone model in 2019." If the new model is more than three kinds, the LCD model may be maintained. However.