Many little cookies will get dropped into the Android 8.1 Developer Preview, active beginning from today and going through December. The APIs, one level up from 8.0 Oreo to level 27, in this first preview are already in final state and only slight tweaks will be made for a second preview next month meant for final testing.
The Nexus 5X, 6P and Player as well as the Pixel, Pixel XL, Pixel 2, Pixel 2 XL and Pixel C are eligible for this beta.
New APIs revolve around neural networks for machine learning libraries and not necessarily apps. Notification bursts will no be signified by annoying, repetitive tones — they will be limited to one ring per second. Other APIs like the one for fingerprint sensors and the one for wallpaper colors will be updated. You can expect more interface tweaks, too.