Apple has made numerous changes in iOS 7, many of which are under the hood. One of the new features that Apple has added to iOS 7 could foreshadow future features that the iPhone will offer, much like these changes have done in the past. Specifically, iOS 7 now allows developers to detect blinking and smiles in pictures, making it easier for photo app developers to detect good or bad pictures.
In iOS 5, Apple added the ability to detect faces in pictures. This was then used by the iPhone's camera app to help with smarter autofocus and better white balance settings. It's possible that the iPhone 5S could wait until everyone is smiling or not blinking before taking a picture. It's worth noting that some Android phones already have a similar feature: they take several pictures in quick succession and select the "best" one.
iOS 7 has also brought the ability to shoot 60 FPS video, albeit at 720p video quality. The new API calls could allow app developers to create better slow-motion videos without losing some of the illusion of motion.
I can't wait to see what Apple comes out with for the iPhone 5S. It will likely be more evolutionary rather than revolutionary, but it appears like it will be getting some cool features and technology.