I have a 6 and I still don't see a reason to upgrade. And people who have the 5 or 5S might be more interested in the 5SE.
Even the biggest Apple Fanboys don't seem to be able to make a case for the new phone. If you are, please do!
I'll be upgrading next month, but mainly because I wanted the 6S and told myself to wait another year for the 7. If I could do it over, I may have just purchased the 6S a year ago, but I feel a lot of people are being overly negative about a phone that hasn't been announced yet.
My primary reasons for upgrading from my 6+:
a) I switched to T-Mobile and their coverage is terrible, so I want a phone that supports the 700 mhz LTE band 12.
b) 1 GB of ram is wildly frustrating (the minimal amount of multi-tasking the iPhone allows you to do goes to **** when your apps close themselves everytime you switch between apps, and because T-Mobile's coverage is terrible, it's frustrating that even though I had a webpage open before I turned off my screen I have to wait for my phone to reload the exact same webpage because it can't keep it in the ram). My phone is also frustratingly slow. This is probably a combination of the old processor as well as the lack of ram.
c) The size of the 6+ is too big for me. It's uncomfortable to walk/run up stairs or to sit in my car with it in my pocket. Ideally I would like a 5.1" screen, but for now I'll give the 4.7" a shot at least until they reduce the bezels on the + model.
d) My iPhone is pretty much the only camera I use and I want a better camera. I own a DSLR but never carry it with my because it's too big.
Upgrading from the 6+ to the 4.7" 2016 model puts me in a little bit of a dilemma as I appreciate the OIS on my 6+ and I really wish I had it for video recording as well. I'm hoping they'll include OIS for pictures and video on the 4.7" model but that is yet to be seen.
Really all of my reasons for upgrading could be achieved by purchasing a 6S, so if I already owned a 6S, I would not be upgrading. I am excited for the things we don't know yet though. Everybody seems to think that because the 7 will have the same general shape as the 6 that it will be the same phone. I'm 100% certain they're not going to get up there and be like "We know you loved the iPhone 6S, so here it is again, only without a headphone jack!". There are obviously going to be great things we haven't learned yet that will start making us more interested. I also am feeling pretty confident it will be water resistant, which I'm excited about as it will ease some concern when the kids are handling my phone by the pool. (I've actually dropped a phone in a toilet and a different phone in a glass of water before myself).
I agree it seems to be a little underwhelming this year when we were expecting a redesign, but it's still going to be better than the 6S, and the 6S was almost enough to make me switch from my 6 but I made myself wait. I'm not going to wait yet another year simply because there will be a better model next year. If the 2017 model is leaps and bounds above the 2016 model then perhaps I'll upgrade again, but there's no certainty all our dreams will come true with that model either.