There has been a confirmation by google, that there will be a continuous support to their google pixel devices but will end after October 2018.
This was published on the support page of Google which confirms that the existing Pixel and Pixel XL devices will get OTA updates on the latest version of android until October 2018. New security patches will also be pushed across these devices until October 2019.
There is a possibility to get android updates just by making a purchase of a newer pixel smartphone.
image credit: techbuffalo