Overall, I was happy with the phone (especially the dual camera in the 7 Plus) and that it was the same design for the third year didn't bother me.
Being on a contract that allowed me to upgrade with no penalties after 12 months, I fully intended to get the 7 Plus but the initial availability problems dragged on.
So it never happened!
By the time the model and colour I wanted were available via my carrier I wasn't in a rush to upgrade any more. Upgrading at this later point would have pushed me further and further behind Apple's release cycle so I decided to just wait for the next one.
The 6S Plus has continued to serve me faithfully and I've not "missed" the newer phone at all.
As my contract ends at the beginning of October I will definitely be upgrading to the 8/X/Edition or whatever it will be called. If the rumoured delays for that model are accurate its availability may just about match my upgrade date.
I just hope they aren't too severe and my carrier can come up with the goods.