As reported by several sites, citing multiple sources, the Korea Herald already provides info about the iPhone 9 and states some details on the display sizes .
The Korea Herald says Samsung has signed a new agreement with Apple to deliver display displays that will be used on 2018 iPhones. The iPhone 9 (or any other name will be chosen by Apple) should be available in two variants , A “normal” and a “plus”. The first will offer a 5.85-inch OLED screen display size, while the latter will mount a 6.46-inch display size, always OLED. The Plus may therefore be larger than the Note 8 recently presented by Samsung
(Source: Korea Herald)