Apple filed a new patent application describing a new hybrid display that can dynamically switch between a full-color LCD (or OLED) to a low power monochrome e-paper. Actually, the screen can be operate in the two modes together - where some parts of the image is seen via the LCD/OLED and the rest via the e-paper. It seems that Apple recognizes the advantages of an e-paper display for actual reading...

The idea is to make a display that has "multiple composite display regions", each made from a transparent e-paper panel on top of an LCD/OLED. The display has several independently activated backlight units, illuminating the LCD panels when necessary (this won't be necessary in an OLED, obviously, as it does not require backlighting at all). On top of the whole device there's a touch layet, too.