Google has started pushing out the Android 8.1 OTA update to Pixel 2 and Pixel 2 XL units running the second Developer Preview build. The update weighs in at 41MB for the standard model and around 43MB for the XL variant. The update will directly bump your device to 8.1 stable channel (meaning you don't have to downgrade to 8.0 first). However, the process does involve a factory reset of your device. It's worth mentioning that devices running Android 8.0 have already started getting the 8.1 update. Not only that, the Mountain View, California based company has also made available...
Source: https://www.gsmarena.com/google_pixel_2_and_pixel_2_xl_units_on_beta_start_getting_android_81_update_as_well-news-28632.php