A few months ago, rumors started to surface of a mini-LED iPad Pro coming this year, and then Apple refreshed the lineup a couple of weeks later without the promised improvements. In fact, it would be easy to argue that this year's iPad Pro lineup was an underwhelming refresh, packing a very subtle processor improvement, LiDAR, camera improvements, and that's about it. The big story was the new Magic Keyboard that has a trackpad, but that also works with the older model of the product.
It seems that the next generation is going to be a more significant refresh, and that will arrive in 2021. Leaksters @choco-bit and @l0vetodream are pointing to mini-LED for the display, along with some other perks like 5G from a Qualcomm Snapdragon X55 modem and a much more powerful A14X chipset.
The mini-LED would seemingly be what Apple is going with instead of OLED, which is what's used on the current iPhone 11 Pro series. While mini-LEDs won't provide the same kinds of true blacks that OLED would, it's still going to be better than a traditional LCD.
As for 5G, it's unclear if the devices will support both sub6 and mmWave frequencies, or if they'll be sub6-only. Sub6 5G might make more sense, since iPads aren't used outdoors as much as phones, and that's the only place where mmWaves work.
Obviously, these products are still pretty far off, so we'll learn more as we get closer to their actual launch.