Xiaomi's MIUI is slated to get a pretty big update to version 9 in the very near future. And a recent leak has shown what to expect from MIUI 9, which includes getting a picture-in-picture mode, as well as split screens, and a screen recorder. MIUI, for those unaware, is the software skin that Xiaomi uses on top of Android, so it's like the Samsung Experience (formerly Touchwiz) or HTC's Sense. Xiaomi updates their MIUI skin very often, and just about all of the changes to MIUI come from their users in their forum, telling them what they need to change, fix or add.
MIUI 9 appears to be getting some rather large features, if this leak turns out to be correct. With Picture-in-Picture mode, users will be able to watch video in a smaller window, while also being able to do other things on their tablet or smartphone. Split screen is exactly what it sounds like. Allowing users to use multiple apps at the same time, by splitting their screen. And the screen recorder mode is also exactly what it sounds like, allowing users to record their screen. This can be very helpful for showing customer support an issue a customer is having, or showing people how to do something, etc. Interestingly enough all of these features are in Android, with picture-in-picture coming with Android O later this year.
Since Xiaomi has not yet announced MIUI 9, it's hard to say when it'll be made official, and also when it'll start rolling out to existing devices. But it is very likely to be rolling out to their existing flagships pretty soon. Including the Xiaomi Mi 6, Mi Note 2 and Mi Mix. MIUI 9 isn't based on a new version of Android, seeing as Android 7.0 Nougat is on MIUI 8 as well as MIUI 7, and MIUI 9 will likely be available before Android O is available to everyone. As was the case with MIUI 7. Of course, Xiaomi may or may not launch MIUI 9 with a new smartphone, and since the Mi 6 was just recently announced, they likely won't have another new flagship smartphone for a few more months.