Android is getting even more Developer Previews, as it moves towards a new 'maintenance release' schedule beyond version 7.0.
Following the official release of Android 7.0 Nougat, there's a lot going on around the Android Beta Program, which started back in March with the first "Android N" Developer Preview build. The short version is this: We'll be seeing more Developer Previews in future versions of Android — and in the short term you might want to stay enrolled in the Beta program, even on the stable 7.0 firmware.
The Android Beta program isn't going away. If you're already enrolled in the Beta program, you'll be among the first to get the final, stable Nougat update. As for future updates, if you stay in the Beta program you'll eventually be updated to the Developer Preview build of the first Nougat maintenance release. (More on that later.) So if you still want to be on the cutting edge of Android, you don't need to do anything after getting updating from Developer Preview
Right now the Beta program is a a reliable way to skip the queue for over-the-air updates and get your Android 7.0 update. And if you un-enroll after taking the final, stable 7.0 OTA, you won't need to factory reset. (In contrast to the situation during the Nougat Beta, where unenrolling on a Developer Preview build would wipe your phone via an over-the-air update from Google.
Android has always had maintenance releases, but they haven't always been this visible.
As we move beyond Android 7.0, the Beta program will evolve into a way to test new Maintenance Releases (MRs) of Nougat.
Maintenance releases aren't new in Android, they just haven't always been this publicly visible. (For example, Marshmallow MR1 landed in December 2015, MR2 in April 2016 — both were Android 6.0.1.) Sometimes these have involved new API levels (and new features for developers to use), and a new Android version number — for example in Android 5.0 to 5.1. Other times MRs have focused on bug fixes under-the-hood tuning, as in Marshmallow.
From Android Engineering VP Dave Burke on the Android Developers blog:
We're moving Nougat into a new regular maintenance schedule over the coming quarters. In fact, we've already started work on the first Nougat maintenance release, that will bring continued refinements and polish, and we're planning to bring that to you this fall as a Developer Preview. Stay tuned!
So maintenance releases in the Nougat era are partly about codifying Android's smaller updates, and partly about giving developers more of a chance to prepare for these changes before they land. With the arrival of new Developer Preview builds in the future, it's more likely that Nougat's maintenance releases could introduce a new API level, and maybe a bump to Android 7.1.
If you stay in the Android Beta program after getting the final 7.0 update, you'll automatically get updates to the MR1 Developer Preview when it's available. Presumably it'll work just like the earlier March-to-August Nougat preview program. According to the Android Beta program site, you'll then receive Android's regular over-the-air updates once the program ends.
Even as Android matures as a platform, the pace of development hasn't slowed — if anything, the new push behind transparent, regular maintenance releases could accelerate things even further.