Apple is reportedly investigating a switch to OLED displays for the iPhone. The company, which has already adopted OLED display technology for the Apple Watch, is said to be talking to suppliers and manufacturers about the switch, which would apparently happen with the 2018 iPhone.
While OLED displays could allow for richer colors, more intense brightness, and better energy efficiency over LCD displays, there are still technical hurdles which Apple needs to clear for an optimal experience. From Nikkei:
There are technical challenges as well. The brightness, energy-saving capacity and other functions of OLED panels tend to degrade over time. Apple has begun consulting with display makers and their suppliers of manufacturing equipment about the technology. The companies will work over the next year or so to see whether those drawbacks can be eliminated and a stable supply of screens secured.
While ultimately Apple may elect to stick with LCD over OLED, it's a no-brainer that they'd at least investigate a switch. One of the advantages of OLED is that it only lights the pixels that you need, so any black interface elements wouldn't use up energy, leading to greater battery life, especially if Apple included a universal night mode.