The design changes coming to Apple's next iPhone(s) aren't much of a secret. As such, it's not difficult to fathom Apple making the devices thinner thanks to new display tech—we've already seen what is alleged to be the final design, and it is indeed thinner than the-already-thin iPhone 5/5S. China Times says Apple will use some engineering magic—moving from two brightness enhancements films to one—in order to ensure the display is thinner than it has ever been.
The thing about switching to a single brightness enhancement film, however, is that the change could yield supply issues, meaning it might be difficult to come by a larger iPhone this fall. The report claims the slack could be picked up by other suppliers, though this is all just speculation at this point. Mass production for Apple's iPhone 6 is set to begin this July, with a launch expected in September—and maybe a launch on Sept. 19.
As 9to5Mac notes, China Times isn't always the most reliable rumor monger, but given all the dummy units we've seen floating around—including the one we have—it's obvious the device will be thinner. Is that due to Apple using new display technology? Could be. I don't think anyone will care so long as the display looks good and the device does notch in thinner than the current iPhone.