I'm still on my Nexus 5. There hasn't been any phone worth upgrading to, that I'm aware of. If I knew that the Pixel would be so over the top expensive I have upgraded to the 5X at the time it was released but I was hoping that skipping a release would be worth it. I wouldn't mind a Pixel though, I'm just not going to pay $1000+ (AUD) for a phone.
For me the Nexus 5 was the last phone that had a great form factor, good enough features and was sold at a reasonable price.