Prior to Google Pixel second generation smartphones, the company used to provide 2 years of Android Version updates. But this trend changed last year and it seems that the new Pixels will get the same courtesy.
As Google has officially confirmed that they will provide 3 years of Android Version and Security Updates to the Pixel 3. So, until October 2021 you are guaranteed to get all the updates.
It’s nice to see that this 3-year update thing is becoming a norm for Pixel smartphones.