When Google pushed out the "final" developer preview for Android 7.1.1 this past week, they did also note that the stable update would be heading out to all supported Nexus devices in December. Now it appears that the update will be heading out on December 6th. Now this sounds about right, as it is the first Tuesday of the month, which is generally around the time that Google pushes out the monthly security update, which means that the December security update will likely be included in this update (no real surprise there). On top of this rumor, it appears that the Google Assistant won't be included in the Android 7.1.1 update. Keeping it exclusive to the Google Pixel and Pixel XL.
Those of you that own the Nexus 6 and were hoping to get Android 7.1.1 for your device, it appears to be "likely". That means it isn't confirmed, but should be available for the device. It would be a bigger surprise to see the Nexus 6 not get the update, considering the Nexus 9 has been getting the developer previews, and it launched with the Nexus 6. The Nexus 6P and Nexus 5X will definitely get the update, as they have been part of the developer preview.
As far as features go, there won't be much different from the second developer preview. Some of the features that are staying unique to the Pixel and Pixel XL include the new navigation buttons, and Google Assistant. It's likely that those fingerprint sensors will also remain on the Pixel devices only. Although developers have gotten them working on other devices including the Nexus 6P and Nexus 5X, but it appears to be remaining with the Pixel devices, officially. Of course, there are also more emoji's coming in Android 7.1.1, not to mention the launcher shortcuts, which will be great for everyone with the Nexus 6P and other Nexus devices, as that feature was exclusive to the Pixel lineup prior to this update.
Now keep in mind that this is a rumor and should be treated as such. But we do know that the update is coming in December, so it does seem fairly likely.