LetsGoDigital has released a new Xiaomi curved display patent which shows no hardware button.
The entire display is covered by display with a small notch noted on the corner of the phone. It also has two stages camera module where the primary lens will be much larger than the other. No hardware button was seen or any front openings such as camera and speaker hole.
The display also achieved almost 90° waterfall style and there are basically zero hardware openings, apart from the very protruded lens.