I have a 13 Mini, and the rumored specs for the 16 make it a pretty competitive upgrade. A18 vs. A15, Action and Capture buttons, 8GB RAM vs. 6GB, etc.
I think the main thing that's going to hold me back is the color options. I don't use a case with my phone, so this is actually relevant to me, and I've had numerous people compliment the dark green iPhone 13 that I have at the moment. It's probably my favorite color that Apple has ever released, and I was totally shocked that the iPhone 15 basically only comes in pastel colors. If they repeat the pastel choices and offer black as the only dark color iPhone 16, I'll probably wait for the 17.