Google has confirmed the availability of future Android updates for its flagship phones, Pixel and Pixel XL, in its recent post on the official support website. One glance at the Android update schedule for the smartphones suggests that Google has insured these devices with feature updates till October 2018 and security updates till October 2019.
The Android maker had earlier announced a similar update schedule for older Nexus devices and it's quite reasonable that the Pixel devices will continue to receive software support for exactly two years from their date of release in the market.
As Google clearly emphasises its intention to offer guaranteed updates in its recent post, it is almost certain that the Pixel devices will also enjoy the privilege of regular platform upgrades like Android O, until October 2019.
[Source: Google]