Google recently released their Android P developer preview, the software can be installed on a number of devices including the Pixel, Pixel XL, Pixel 2 and Pixel 2 XL.
The new developer preview is not available for the Nexus 6P, the Nexus 5X or the Google Pixel C tablet. It would appear that these devices will not be getting the Android P update.
Google previously said that the devices above would be supported for two years. When the next version of Android comes out later this year, it will be three years since the devices above were released.
So it looks like the Oreo update is the last major release that the above handsets will get. The devices are expected to continue to get the monthly security updates this year.
Source GSM Arena