Peter Misek, an analyst at Jefferies, just returned from a trip to Asia, and he came back with some pretty wild Apple rumors. Peter claims that there are several Apple prototypes "floating around" - including an iPhone with a 5.5" 2K OLED display, a foldable iPhone with a 4" OLED (that opens into an iPad mini) and of course smart watches and wearable devices.
It seems highly unlikely that Apple will adopt an OLED display in its next iPhone. Apple does not like to rely on a single supplier as currently only SDC can produce AMOLED in any meaningful volume. And even SDC does not have the required volume to supply Apple. The foldable iPhone is even less likely and is probably just speculation (or, as Peter himself says, this may just be Apple trying to confuse its competitors).