Xiaomi just announced the MIUI 10 the new update to MIUI 9 earlier last month and also launched the beta update to most of the Xiaomi devices. With MIUI 10 launched recently, Xiaomi has already started working on the successor with MIUI 11.
In the latest Xiaomi MIUI 10 review, the company has mentioned the MIUI 11 for the first time. The new MIUI 10 was basically made for the present 16:9 aspect ratio display and not for the current trend with 18:9 and above which we saw on most of the mid-range and high-end smartphones but Xiaomi has tweaked the software to make it compatible with devices featuring display notch.
Xiaomi further tells that MIUI 10 is not bad at all but will work better UI with next iteration MIUI 11. We can expect more user real need-based design on MIUI 11 and will not have any major changes in terms of UI when compared with MIUI 10. Anyway, MIUI 11 will not arrive anytime sooner than 2019.