A few days ago Xiaomi has started releasing the beta version of MIUI 9, its latest user interface based on Android Nougat, on the first Xiaomi phones. The first phone released with Android 7 out of the box is Xiaomi Mi6, followed by Xiaomi Mi 5X (announced a month ago) and Xiaomi Redmi Note 5A. But in the mean time, Google has announced Android Oreo, the 8th version of its operating system.
Xiaomi phones are still going to get Nougat, so we do not know when Android 8 will come. But if you have a Xiaomi Mi3 or Mi4 you can already try it, even if Xiaomi will take a long time to bring it on its devices. A developer called Shakan_mik3 from XDA Developers has just released the first ROM for Xiaomi Mi3 and Mi4 based on Android Oreo.
If you have one of these two phones and you want to install it, first of all you need to download this TWRP, then you have to download the ROM, and at last you need these Google Apps if you want to install Google Services. It is recommended to do a Wipe System + Wipe Data + Wipe Cache before flashing the new ROM on Xiaomi Mi3 or Mi4.