Let's not get too carried away here, Mini LED is not a huge deal. Mini LED is essentially like local dimming technology on large displays. It works well but it's not a huge improvement when compared with technology like OLED displays.
I think most posters here are thinking of MICRO Led which is a totally different technology, of which I don't see coming to the iPad for a few years (maybe 2025). That tech allows each LED to have it's own light source so you can have better control of contrast and overall brightness.
Micro LED displays are VERY expensive right now and are limited to larger displays. Currently they are being used as wall displays that can be assembed out of multiple micro led displays put together. The problem with micro led right now is the production process is tedius and it can take a few weeks just to put together one display.