Back in March 2016, Google released the "Android N" Developer Preview for a few supported devices. The aim of the program was to allow the company more time to incorporate developer feedback, and to submit the final version of the release to hardware manufacturers for early testing.
Google has now announced that the Android Nougat Beta Program is complete, and that a Beta for the next version of the operating system will be released soon.
Before the official release of Android 7.0 Nougat to the general public, five Developer Previews were seeded out to those willing to test early builds of the operating system on their devices. After the general rollout of the aforementioned iteration of Android, Google also released two versions of Android 7.1 to users in the Developer Preview.
However, now with "Android O" on the horizon, Google has concluded the Beta Program for Android Nougat, saying that:
Thank you for your interest in the Android Beta Program! The beta for Android Nougat has concluded, and all devices that were opted in have been updated to the current public version. If you are still running a beta version of Nougat you may download the latest full OTA image for your device and sideload it. This will not wipe your device. We'll update this site when the Android O Beta Program begins.
In the meantime, you're welcome to talk to other interested users by joining our Android Beta Program G+ Community.
The first Developer Preview build of Android O was rolled out a couple of months ago, and is currently available as an alpha release. The Beta Program is scheduled to begin this month, with the general release slated for Q3 2017.