In May 2017, Google announced that it has partnered with "one of the leading OLED makers" to develop a high-end VR display. Google is now set to demonstrate this display at SID 2018 in May.
The new Google-designed display is a 4.3" 18Mp (1443 PPI, probably around 5500x3000 resolution) VR display featuring a refresh rate of 120 Hz. This will be the highest-density OLED display ever (not counting OLED-on-silicon microdisplays). Current VR AMOLEDs in production reach only about 600 PPI.