The MIUI 12 stable rollout for Xiaomi devices in China included in the third batch or phase of the company's update roadmap could begin by October depending on how the second-batch rollout progresses. Smartphones that are part of the third batch include the Xiaomi Mi Mix 2, Mi 8 SE, Redmi 7, and Redmi Note 8.
https://www.notebookcheck.net/MIUI-12-could-start-arriving-on-third-batch-Xiaomi-smartphones-like-the-Redmi-Note-8-and-Mi-Mix-2-in-October.484947.0.html