Now we have a better idea as to why Google has decided to stop supporting the good ole' Nexus 5. According to a tweet by LlabTooFeR, Qualcomm will not be updating any graphics drivers for the Snapdragon 800 or 801 Processors. This means that any devices using either of these processors will not receive an update to Android 7.0 Nougat.
Other than the HTC One M8 which was mentioned in the tweet, here's a list of other popular devices that won't see Android Nougat if this rumor is true:
Just because a device isn't officially supported by Google, the OEM, or even the processor manufacturer, doesn't mean that it will need to head straight to the graveyard. That's evident in the fact that there are already unofficial builds of Android Nougat for both the Nexus 5 and Nexus 7 (2013), which both were left in the dust with this year's Android updates.
It's not upsetting that Qualcomm isn't releasing any new drivers for these processors, as the devices are now almost 3 years old. It just means that you'll need to update your devices sooner rather than later.