As per news yesterday, HTC has uploaded the Nougat files to its download page. In case you haven't received the OTA update yet you can go ahead and check it yourself. Also you would need HTC Sync Manager installed.
Mo Versi, the VP of Product Management over at HTC - USA, has announced via his Twitter account that starting today, unlocked versions of the HTC 10 will start receiving a software update to the latest version of Android Nougat. Whether the update would be available just in the US or globally is not mentioned in the tweet.
Based on the tweet, we assume that the carrier versions of the device too would start receiving the update soon.
After the HTC 10, the company will release the Nougat update for some of their other devices as well. Since the newly announced Bolt. known as the 10 Evo in Europe, already runs on Google's latest version of OS, we assume the next devices to receive the update should be last year's flagship HTC One M9 and the HTC One A9. However, HTC has not given any info on when the update for these two devices will be ready.