Apple has been with the same design from past 2 years which commenced with iPhone 6 & 6plus the 4.7 & 5.5 inch models respectively.

Its the 10th Anniversary for iPhone in 2017, Should be something special right? 

The iPhone 7 is almost similar to the iPhone 6s & 6 on the design status. iPhone 8 is expected to come in three variants 4.7, 5.0, 5.5 inch 

The phone is expected to have the front entirely made of glass as well as the back, where a metal frame will hold it together. Nikkei, one of the most reliable sources for Apple leaks, suggest that the phone will have glass faces designed by Biel and Lens. It is important to note that the last time Apple used an all-glass unibody, it was on the iPhone 4s.