When you take into account the amount of users who have held onto the iPhone 6, 6s and 7, Apple will indeed have a super cycle. Lets not forget about those who are likely on a 5s or SE interested in moving to larger model. There are the fanatics who upgrade every year, but they are more likely a niche.
For me, I see this as a 'S' year and I am more interested in next years model, which will probably be the first 5G iPhone.
Count me as one who would gladly switch to an updated SE phone from a 7. I know it's too much to hope they keep the audio jack.