Xiaomi's MIUI operations manager made a post today about the Mi 4 and Mi Note receiving the Android 6.0 Marshmallow soon. This means these devices will be the first Xiaomi devices to get the new Android OS. MIUI won't change, which means it stays at version 7.
This comes just a day after Microsoft released the Windows 10 ROM for the LTE variant of the Mi 4 smartphone.