Reports from Korea suggest that Apple is considering to use an OLED display in the 2018 iPhone. The main reason that is quoted is that Apple wants to improve the saturation and brightness of their mobile phone displays.
According to the reports, LG Display may be chosen as the main OLED supplier. LG Display's current small-sized OLED capacity is very small, and so the company will convert its LCD facilities in Gumi to produce OLED displays, with mass production reached by the end of 2017.
If this report is true, it's highly likely that Apple will choose a flexible plastic-based OLED. LGD does not produce glass-based small-sized OLEDs (they actually did have a production line but LGD ceased production in 2011), and plastic-based OLEDs have many advantages (they can be curved or maybe even folded, and then are thinner and lighter and more durable). Also Apple is already using LGD's plastic-based flexible OLEDs for their Watch wearable.
I'm a bit skeptical about rumors that try to predict Apple's display choices three years in advance. Then again this rumor has been reported on many major web sites, and it makes sense that such a decision by Apple will be taken a few years in advance, so I thought I'd better post it on OLED-Info as well.