Xiaomi's OS update cycle differs from the conventional cycle followed by most other OEMs. In addition to base Android versions, Xiaomi devices also rely on MIUI updates for getting new features and stability improvements. This often means that features across devices are reliant more on the MIUI version than on the Android version of the device. On the other hand, the base Android version update definitely takes more time to arrive on the device as compared to other OEMs, but that is to be expected considering how heavy MIUI is as a UX skin.
Nonetheless, Xiaomi remains committed in bringing over the latest Android version to more and more devices in its portfolio. The Android Pie update was promised for devices like the Xiaomi Mi Mix 3 and the Xiaomi Mi 8, and these have been delivered accordingly.
Now, Xiaomi has promised to bring over Android Pie for Xiaomi Mi 6X, the Xiaomi Redmi Note 5 (Redmi Note 5 Pro in India), the Xiaomi Redmi 6 Pro and the Xiaomi Redmi S2 (Redmi Y2 in India), with the internal beta estimated to be ready within Q1 of 2019. While this news does not give a concrete timeline on when the stable update arrives for devices like the Indian Xiaomi Redmi Note 5 Pro and the Redmi Y2, it does imply that both the devices will receive an official Android Pie update, eventually.
If you would like to participate in the internal beta program for these devices, head on over to the Beta Sign-Up page. Keep in mind that beta software is called beta for a reason, so only sign up if you know what you are walking into. For those unsure, keep calm and wait for stable Pie.
Xiaomi Redmi Note 5 Pro XDA Forums Xiaomi Redmi Y2 XDA Forums