Hmmm. If you didn't get it so far, I doubt they will ever release it for your phone. Which phone are you using, if it's not a secret?
Redmi Note 3 Pro since I needed a dual-sim phone. It was a recent purchase and Xiaomi's offerings are a bargain. Waiting for MIUI 8.
Xiaomi make some very nice phones. I've got Chinese phone too, a Meizu M2 which will amost certainly never get Marshmallow or anything released after that. It came with Meizu's Flyme OS running on top of Android 5.1, but since then Meizu switched from Android to Yun OS - which is a Chinese fork of Android (that is compatible with Android). This is not a big deal to me, as while I no longer have Android on my phone, I do get a OTA update to the latest beta of Flyme OS every week.
It sounds like Nougat brings changes that could impede a user's/admin's ability to inspect their own traffic and verify that it is safe. I didn't carefully read through all of this, but some of you who intend to use it may want to: https://android-developers.blogspot.com/2016/07/changes-to-trusted-certificate.html https://news.ycombinator.com/item?id=12061320 (link to above + discussion)