Apple filed a new patent that describes a fascinating elastic haptics display. The idea is that the screen can not only provide tactile feedback (using vibration, etc.) but change its shape to form real 3D buttons, markings and even maps. Pretty cool.
In order to create such a display, Apple needs a flexible panel - and indeed they specifically mention a flexible OLED panel in the patent. Apple does say that any suitable flexible display panel can be used, for example graphene based display. But it seems that OLED is the most mature technology when it comes to such flexible displays.