Google Nexus devices will get their January Android security updates anytime now
Non-Nexus devices eventually get these Android security updates (Samsung, LG, Motorola, and HTC are actually moderately fast to bring these updates to their high-end devices), but Google's own Nexus line-up has the privilege of getting these security fixes first, since Google is responsible with sending the updates, and not the carriers.
The Google Nexus 5 support page on Sprint's official website, as well as the Nexus 6 support page on Verizon's website say that software version MMB29S will be released today for the corresponding devices. The Nexus 7 support page on Verizon's website lists software version MBB29O. The same security update is probably on its way to the Nexus 5X and the Nexus 6P. At the moment, the factory images have yet to show up on Google's website, but they probably will over the next few days.
The change logs for the new security update do not mention any new features or improvements, as the new software is still based on Android 6.0.1, the most recent version of Android currently available.