Good news for AT&T Nexus 6 as the new firmware update has been rolled out via OTA and this update contains January security patch which is the latest one.The version number of this update is NBD91W. This update will reach your region as the update is rolling out region to region.
As I already told you that this update has been already rolled out and will reach you region wise, in case you have rooted AT&T Nexus 6 or you have unlocked the bootloader, then you may not receive the update. So either you can unroot your and lock your bootloader to get the update or you can manually download and install the NBD91W update on your AT&T Nexus 6.
For those who haven’t rooted their AT&T Nexus 6 can check for the update by going to their Mobile’s Settings> About Phone> System Update and search for the update if the update is listed then go ahead, download and install it.
The best part is that this update is based on all new Android Nougat 7.0. Android Nougat contains many amazing feature, stability improvement and much more so if you want to experience all new feature of Nougat then, You have to update your mobile as soon as it reaches to you.
Keep in mind before updating the firmware make sure you have full charged or more than 50% of battery. The update size may be big so also make sure to connect with Wi-Fi as it is a better option.