iPhone 7 just launched, but the rumors regarding iPhone 8 have already started to hit the web. Some sources of 9to5Mac state that the work on next iPhone iteration has already begun and the main focus is on changing the design.
Rumors further state that the iPhone 8 will look a lot like iPhone 4, which is arguably the best looking iPhone to launch till now.
Overwhelming demand of iPhone 4 even years after its release has made Apple realize that they need to go back to the old design. However, it will not be a complete ditto copy as there will be some changes, but what those changes would be and how will they impact the overall design remain a mystery.