updated 04:14 pm EDT, Tue July 9, 2013
Would keep iPhone up to par with Galaxy S4
Code hidden in the iOS 7 beta suggests that both iOS and a future iPhone will get support for 120fps video recording. Prerelease the feature is referred to as "Mogul" mode, but any other details -- such as what resolution it might operate at -- are unknown. Shooting at such high speeds allows for smooth slow-motion effects.
An iPhone with an improved camera would be needed for the mode, but this may have been presaged by a couple of factors. Apple has already announced 60fps capture as an iOS 7 option, a speed double that of the iPhone 5. Samsung meanwhile already supports 120fps on the Galaxy S4, which could make its addition to the iPhone simply a matter of keeping up.
Apple does however have a history of leaving in code references for features that take time to materialize. Bits of a panorama feature were found in iOS 5, but didn't actually become functional until iOS 6.