I'm supposed to upgrade my iPhone 6 in February 2017. On the one hand, I don't really want to wait until September 2017, as my current phone is quite slow and I'd really appreciate faster touch ID and 3D Touch.
But it looks like the iPhone 7 will be really, really boring, and hardly an upgrade, while waiting 7 months would lead to a massive upgrade... but that's an extra 7 months after already having the 6 for two years.
I really wish Apple would keep its tick-tock cycle. I like being on the non-S cycle, while skipping to the iPhone 8 will presumably place S-upgraders on the non-S path, and vice versa.