https://www.theverge.com/circuitbreaker/2017/8/24/16195756/google-pixel-2-launch-date-rumor

On October 5th, 2017, a year and a day after the October 4th, 2016, unveiling of the Pixel and Pixel XL, Google will take to the stage again to announce its Pixel 2 generation of devices. This is according to prolific leaker and spoiler of well-kept secrets Evan Blass, who has tweeted the date along with confirmation of the processor spec for these new phones:

Google's second-generation Pixel handsets, powered by Snapdragon 836 SoC's, will be unveiled on October 5th.