We've received quite a few emails in the last 24 hours excitedly pointing to the following branch in the Nexus 5's repository on the Android project as evidence Google plans to bring Android N to the phone. Specifically, there is a branch in the Nexus 5 repo called "android-n-preview-1" - which many are taking to be a signal that Google is actively developing Android N for the Nexus 5.
Unfortunately, such interpretations are not supported by the existence of this branch. As a result of the tools Google uses as part of building Android, pretty much any device that is currently supported (note that current support does not mean future support) by Google will generate branches for new versions of the operating system regardless of whether or not they'll actually get them. And to be clear, this branch also in no way suggests the Nexus 5 will be added to the N preview - you can basically be assured that it won't. But if you want a real-world example that is illustrative of this phenomenon, let's look at the Nexus 4.
The Nexus 4 has a branch for "android-m-preview-2." The Nexus 4 was never part of the M preview, and it was not upgraded to Android 6.0 Marshmallow. Google never said it would be, either, and yet: at least some corners of the internet (sorry, we didn't mean to pick on a specific website, we just needed an example) took the existence of the initial "android-m-preview-1" branch as evidence that the phone would get M, and were later sorely disappointed. So please, let's not jump to the same unsupported conclusions again.
Now, do we know the Nexus 5 won't get Android N? Absolutely not. These decisions tend to be made on a business, rather than technical, level, and Google may still well be deciding if the Nexus 5's existing user base warrants an upgrade to N versus the resources necessary for supporting it. That's a crystal ball we wish we had, but at this point, our guess is as good as yours. It will be well outside of the 2 years of OS update support Google promised by the time N is officially released this summer, but we wouldn't dismiss the possibility of N out of hand just on account of that timeline.
The Nexus 5 may very well get N. It also may very well not. What's important to know is that this reference in the Nexus 5 repo to N does not sway the likelihood of those outcomes. It's little more than a technical consequence of the manner in which Android is maintained. So, let's just wait and see - we'll certainly be among the first to tell if you we get reliable information on the Nexus 5's future OS version support status.