We got a tip earlier today from a user whose Sony Android TV gave him a message about an upcoming update. The message does not explicitly mention Nougat, but among the features listed are some that are exclusive to Android 7.0. Unfortunately, we don't know exactly when the update will hit, but the included information says that it is scheduled to begin after 05/2017.
Among the features listed are a few that stand out as being indicative of Nougat. The changes mentioned include Settings screen improvements to allow you to continue watching while making changes, and that's a feature we know for a fact was only included in Nougat. Picture-in-picture mode with simultaneous app use is also exclusive to Android 7.0. So, even though the changelog doesn't mention it by name, we still feel pretty confident that the update is for Nougat.
Sony confirmed back during CES this year that they were planning on releasing an update like this soon. However, Sony also made similar assurances during 2016's CES that their full line of 2015 and 2016 TVs would see Marshmallow. It still took Sony until last December — almost a year later — and even then they never met their full promise. Only some 2015 model TVs actually saw the update. So while Sony might say that they are planning on releasing Nougat for their line of Android TVs soon, I'm still more than a little suspicious. I'll believe it when I see it, Sony.