Google has now released Android O Developer Preview 4 for all the developers and users part of the beta testing program. This is the final developer release from Google before the release of stable Android O for all end users worldwide.
This latest developer preview is basically the last chance for developers to make sure that their apps are ready for Android O and work smoothly on the next major Android version. It comprises of latest bug fixes, optimizations, and final APIs which is the API level 26 which made its debut with the Android O Developer Preview 3 next month.
In the official announcement to developers, Google said:
The app should run and look great and should handle the Android O behavior changes properly — in particular, pay attention to background location limits, notification channels, and changes in networking, security, and identifiers.
So if you are already a member of the Android Beta Program, you will receive the latest developer preview release as an OTA update on your enrolled device. If you are not, you can either become a member or download necessary files to flash them manually on an eligible device. This list of devices includes the Google Pixel, Pixel XL, Nexus 6P, Nexus 5X, Pixel C, and Nexus Player.