Stable MIUI 12 updates for the Mi 10 and Mi 10 Pro have already arrived for Chinese versions of Xiaomi's latest flagships. The same cannot be said in other countries though, as some people would have discovered today.
https://www.notebookcheck.net/Stable-MIUI-12-is-not-headed-to-all-Xiaomi-Mi-10-and-Mi-10-Pro-handsets-just-yet-as-EU-and-Indian-models-receive-underwhelming-new-updates.478505.0.html