Update [April 25, 2017]: HTC is currently rolling out a new update to the One X9. Identified as build 2.23.400.2, the update brings additional performance and stability improvements. Since the update weighs in at 687MB it should include a few important patches and iron out bugs from the previous build too. Before downloading the update, ensure that your data is backed up and that you device has at least 50% charge.
The release, a pretty big one, contains bug fixes and system performance enhancement. The mid-range X9, an early 2016 release, is most likely to receive Nougat update in early 2017. The Helio X10 powered device is currently running on Marshmallow.
Do upgrade your device to the latest software version, for it will bring down your security vulnerabilities and enhance performance on your favourite device. If you haven’t received a notification yet, you may want to manually check it from Settings > About Device > Software updates.
HTC is expected to start Nougat rollout for the 10 soon, while the screenshots have already been leaked on the web. It could be followed by the One M9 Nougat upgrade, with One A9 being last of the three devices HTC promised to deliver Android 7.0 update on before December-end.