Alike the OnePlus One, OnePlus 3 is too catching up quickly within the community for extended support. Thanks to OnePlus for releasing its sources in time which made it possible. An unofficial port of CyanogenMod 14.0 which is at its alpha stage right now with most of the things not working.
Listing the things not working, your phone will be a WiFi only device without calling, camera and dash charging. Even the alert slider will not work but you will be able to install apps from Google Play Store using the WiFi. Bluetooth, GPS, and NFC are left intact in working condition.
The amount of interest flowing through the forums for Android Nougat I believe devices initially left out, namely Nexus 5 and Android One would eventually get it working somehow if it’s not for a stable build. With an extremely early build already live for the OnePlus 3, we have hopes for a stable release to arrive soon. To follow-up on the updates, check out this XDA thread here – http://forum.xda-developers.com/oneplus-3/development/rom-t3454940