We already knew that the new Marshmallow 6.0 update is coming to the Mi 4 and the Mi Note smartphones and from now on we can add another phone to that list - the Mi 3.
It is revealed update will weigh 518 mb and it won't bring a new iteration of the MIUI interface (it means it stays at 7).
Update is still in beta, so it might still have some bugs. The final version will be available in a few months from now.