ZTE Axon 7's Android Nougat update is delayed, but should be released this quarter
According to ZTE Germany (which made the initial statement), the Nougat update is being delayed "a little" because, in its current state, the software on the Axon 7 does not meet "quality requirements." The company says the update should be released before the end of this quarter, so it may arrive as late as March.
ZTE recently opened a Nougat beta program for Axon 7 users in the US, but it's no longer accepting registrations. Thus, even if you'd be willing to test a beta version of Nougat, you still have to wait until ZTE pushes the update to everyone. On the bright side, the update will include Google Daydream support, which likely means you'll get Android 7.1.1 directly, not Android 7.0.
source: ZTE Germany (Facebook) via Reddit