Since the third iPhone ever produced, Apple has been following the same naming scheme. Every other year they release a new iPhone with a different design and new features. Since it’s a large update, that iPhone gets it’s own number. The years in between, there is a smaller iPhone update which gets an “S” after the number.
With the iPhone 7, we saw a smaller update to the phone. There was a minimal design tweak and a few new features. With rumors going around about what we’ll see in the next iPhone, coming September 2017, it seems like this is going to be a major update. Because of that, many people are thinking that we’ll skip the iPhone 7s and go right to the iPhone 8. It won’t be following the same naming scheme as the previous years but there might be some more features.
The name of this device is not yet known, but based on what we’re hearing, it could very well be the iPhone 8. Another possibility is that Apple will launch an iPhone 7s and everything that we’re hearing now is for the 2018 iPhone.