According to a report from the Wall Street Journal, Apple will move to an all OLED iPhone lineup in 2020. That means that the 2019 successor to the iPhone XR will be the last iPhone to have an LCD. Such a move will allow for a "more flexible handset design" which could be a hint at a completely redesigned iPhone lineup in 2020, perhaps even at a foldable iPhone. It's well-documented how hard it was for Apple to create the liquid retina display on the iPhone XR, needing to experiment with the backlight design to extend the LCD to the edges. And even then the LCD on the iPhone XR has...
Source: https://www.gsmarena.com/wsj_2019_iphone_xr_will_be_the_last_lcd_iphone_oleds_are_the_future-news-35178.php