I've got the 6S and it is in perfect condition so that is a major factor. I've recently switched to Bluetooth headphones and am never going back. So lack of jack is no issue for me.
But if price starts at $649 and since even 32gb is really too small for me, if the next size is $749 I will need to think about this. That is a lot. I don't think a phone is a minor upgrade just because the case doesn't change. The 6s was a nice upgrade from the 6 and I'm glad I got it. But I don't see how the CPU upgrade can make an impact this year. The A9 in my 6s is already very quick. Battery life is already easily full day even if I have a really late night. I'd need something like 3D Touch to make a difference. Maybe image stabilization on the camera will come in the non plus size that I prefer. But what else is there in the rumors?