Today Xiaomi India announced via their Twitter handle they have begun testing of their alpha build of the Mi5 Nougat update, within the MIUI 8. It was expected that the first Android 7.0 build would come with MIUI 9 UI baked in.
If you own a Mi5, you have until November 21 to apply for the Android 7.0 Nougat alpha build. This is testing for Chinese build BTW, while the Nougat alpha build for global users is going to go live next week, Xiaomi says.
To be eligible, you need to have Mi5 of course, and be an active member of MIUI forums, and have the QQ app and are willing to discuss things up in the QQ app. So, maybe you gotta make do with Mi5 CM14 ROM for a bit of more time.
If you successfully registered, then Xiaomi will PM you a link on November 21, which is your download link for Mi5 Android 7.0 Nougat update in alpha version.
Xiaomi has already provided the installation guide for the Mi5 Nougat alpha build, which can be found here, while the bugs can be reported here.
The Nougat update for Redmi 3 and 3S and older devices like isn’t expected, BTW.