I kinda doubt they're gonna let issues like that, ones the majority of both people who didn't upgrade and those that did list as their main problems with the current models. Considering Google is directing app devs to start making their apps work with the 18:9 aspect ratio seen on the G6 and the S8 (18.5:9 but still) it's very likely Google is planning on implementing that on their device as well. And if what they said about the design of the Pixel is true (it was rushed after Huawei backed out when it was apparent their collaboration with Google wasn't going to garner them any publicity for the hardware) then this next device should be more in line with what Google wanted the Pixel to be from the start. Many are saying the Pixels are essentially a rehash of the HTC A9 so that explanation makes sense.
While I fully expect Google's Pixel sequel to be better than the original, it's not to say that it couldn't still be a disappointment. People build things up in their head and when it doesn't come out exactly as they want, it's a failure. I moved on to the Pixel, the regular one because I wanted a smaller device before I got the 6p but for me the 5x had too many tradeoffs, but I still have my 6p. I find myself using it more like a tablet replacement and a backup if my primary device goes down. But if they dropped the regular Pixel and only offered phones 5.5" and larger, I'd probably have to look elsewhere. I'm not saying that no one should use a larger screen device, I see the benefits. But I find that I don't miss the size of the 6p in the least, it's more usable for one handed operation and with the smaller screen and lower resolution, it gets much better batter life than my 6p ever did with a much smaller battery.
Hopefully the news that Google is going to offer three Pixels this year means that maybe they'll cover everyone's needs. A 5" device for people like me, a 5.5" device for those who don't like the smaller device like the regular Pixel but also don't want to go to something along the lines of the Nexus 6, and a 6" or larger device for those who thought the Nexus 6 was only a good starting point. Keep the internal specs, CPU, GPU, RAM, storage, etc., the same across all devices and they could really have something.