I've had both the iPhone 6 and the iPhone 6s, and I'm definitely in for the iPhone 7.
That said, the iPhone 6/6s is still a bit too big for my taste. I'm used to it by now, but I'd love a new iPhone that's a good bit shorter, lighter, and thinner.
If the iPhone SE had the exact same specs as the iPhone 6s (which it won't) and was the size of the 5/5s, I would absolutely sell my 6s and get the SE.
I was really hoping that the iPhone 7 would get a big redesign and make the entire phone shorter/lighter/thinner, but it looks like it'll be staying the same same length. It'll certainly be thinner, not sure about the weight.