Xiaomi will launch both the Xiaomi 12 series and MIUI 13 at its event tomorrow. The company has now also confirmed that the new flagship phones will come with MIUI 13 pre-installed, with prior information indicating an imminent OTA rollout starting with phones in the Mi 11 and Redmi K40 series.
https://www.notebookcheck.net/Xiaomi-12-to-launch-with-MIUI-13-pre-installed-Xiaomi-confirms.588955.0.html