First new Nougat beta build will be distributed in the fall.
Android's release schedule has historically been all over the place, but for the last few years we've gotten roughly one major release per year, occasionally punctuated with medium-sized maintenance releases, minor feature updates, and monthly security patches. Now, the latest of Google's blog posts about the Android Nougat release suggests things will become more predictable in the future.

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!

This strongly implies a quarterly-ish release schedule for new versions of Android rather than one big announcement followed by a major release a few months later (like we've seen with Lollipop, Marshmallow, and Nougat). And the public beta program that delivered new Nougat betas to interested Nexus users all summer is going to live on, delivering a steady drip of beta software all year long.

A regular release schedule would more closely track what Apple and Microsoft are doing—both companies still tend to save major changes for big updates that hit once or twice a year, but the Apple Beta Software Program and Windows Insider program both supply beta testers with new builds throughout the year. Google does itself this with Chrome OS, which offers stable, beta, and developer release channels that all get updated continuously and gradually rather than all at once.

News about these maintenance releases helps explain some of the Nexus rumors we've seen reported in the last few weeks, especially the reports that the "Nexus Launcher" is apparently targeting a version of Android with a higher API level than Nougat (the build in the rumors is API level 25, Nougat is 24). A move to quarterly releases would start bumping that API level and Android's version number more quickly than we've seen in the last few years.

The Android ecosystem's fragmentation is still the elephant in the room, and it's something Google rarely addresses when it publishes news about new versions. Android phone makers are notoriously bad at getting major updates out to their phones in a timely manner, and any hardware more than a year or two old is lucky to get updates at all. A few of the major players do a decent job of keeping up with Google's monthly security releases, but many phone makers don't. A regular quarterly release cadence could help phone makers schedule and plan their updates better than they currently do, but any update chain that still relies on phone makers and cellular carriers is still going to deprive consumers of new features and important security patches.