As per iHelp, the upcoming iPhone 8 main camera can record 4K videos @60fps.Here is the screenshot for the same which defines code, [CAMCaptureCapabilities isBack4k60VideoSupported].
There is one more screenshot which claims even the front camera can record 4K videos at 60fps.
So if it comes with both front and rear camera which can record 4K videos at 60fps then it will be the first smartphone to have 4K videos support at 60fps till date.And it might give tough competition to HTC U11, Samsung Galaxy S8 and Lg G6 which all had 4K recording @30fps and front camera can record up to 2K. So we have to wait for Apple iPhone 8 to arrive and test its camera results with all other flagship, whether it out performs better than most of the Android flagships?