Although the first official build is not ready yet, the Android 7.1 Nougat-based LineageOS 14.1 is now available in a nightly/experimental stage for a few devices, including the Nexus 6P and 5X, Moto G4 and G4 Plus, Nextbit Robin, and Xiaomi Redmi 1.
http://www.notebookcheck.net/LineageOS-14-1-now-available-for-Nexus-and-Moto-handsets.193094.0.html