MIUI 12 only just landed for most of Xiaomi's lineup but the company is already set to unveil the next iteration of its skin. It's MIUI 12.5, though, not MIUI 13 as one would expect, and it could very well be launched on December 29 alongside the Mi 11 series.
https://www.notebookcheck.net/MIUI-12-5-potentially-set-to-debut-next-week-alongside-the-Mi-11-series.511018.0.html
Xiaomi are a shambles of a company. A shadow of what they were.
In just over a year I have had 3 updates on my Mi9.
The first broke my phone for 11 days and needed factory reset.
The second made it more buggy.
The third bricked the phone and required factory reset.
Endless non update related issues remain still broken, so these broken updates don't even fix issues that have been there since day 1, they add issues.