Google is reportedly working on a new "mobile" device that is going to be running on the new Qualcomm Snapdragon 710 chipset, that is being targeted with a release of early next year. This information comes from Roland Quandt who has been very accurate with insider information like this in the past. According to his thread of Tweets on Twitter, he believes this might be the upcoming mid-range Pixel smartphone. He also noted that development on this only started a month ago, which is likely why it wouldn't be launching this fall with the Pixel 3. Quandt also doesn't know much about the specs of the device, or the name. The only real information that he has is the fact that Google is working on a device with the Snapdragon 710 inside.
The Snapdragon 710 is a new chipset from Qualcomm, and it's part of a new line of chipsets at that. The Snapdragon 700 lineup is slated to be a mid-range chipset for premium devices. Think of something like the Moto G5S Plus from last year, which had somewhat high-end specs, but still ran on a Snapdragon 625. This new chipset is going to offer better performance, with better battery life, than anything in the Snapdragon 600-series, though it is not quite as good as the Snapdragon 845, but it is cheaper.
Google has been rumored to be working on a mid-range Pixel smartphone for over a year now. The company was rumored to be launching a mid-range model with the Pixel 2 and Pixel 2 XL last fall, but that did not happen. Now the rumors have started flying once again. Now, if Google does not launch this mid-range Pixel smartphone with the Snapdragon 710 inside, that doesn't necessarily mean that Quandt was wrong here, it could mean that Google has scraped the project, or perhaps shelved it until next fall. There are many projects that go on inside Google (and every other company) that gets leaked but never sees the light of day.