Android 10 had a lot of battery use optimization over 9 - and my charge-to-charge time shows it. With the 4 coming with 10, it shouldn't be that big an issue, but it's still too small for my taste. (Not that it would get me to jump back into the Samsung firepit. I had too many Samsungs go bad during warranty and told it was my fault - when it wasn't. My Pixel 2? They had me send them a debug dump to diagnose a problem, and I had left the phone rooted ... so the dev I was working with just asked me to unroot and send him another dump. [Which I understand - about 25% of the dump was lines thrown in because the phone was rooted, and he wanted the smallest dump possible.])
I just want to see a Pixel with something new. The P2 with the latest Camera 3 port isn't very far below the 4. And I'm still getting updates to 10. I might buy a 5 if they come out with something (other than WiFi 6, which doesn't interest me, because I have no need for it). Or stay on 10 until the 6 comes out.