On Aug. 5, Google released new system images for the Nexus 4, Nexus 5, Nexus 6, Nexus 7, Nexus 9 and Nexus 10. (androidcentral.com)
Well, first, Google is pushing the final version of Oreo to those in the Android Beta Program today, and it's also published new system images which can be manually flashed onto supported devices. (neowin.net)
The script should flash your device with the new system image. (howtogeek.com)