Nicholas Furno reporting for iGeneration (originally in French):
Although the 2021 iPad Pro 12.9 inches is largely similar to the 2018 and 2020 models, the new tablet stands out in one respect: it is precisely 0.5 mm thicker. It doesn’t seem like much, but it’s enough for Apple to have adjusted its Magic Keyboard, the keyboard with trackpad dedicated to iPad Pro. And according to the documentation provided to the Apple Store that we were able to consult, the old Magic Keyboard is not compatible with the large iPad Pro of 2021.
The Verge confirmed the discovery.
This is a disappointing development, because while there is a new 12.9-inch Magic Keyboard that will work with the older iPad Pro models, if you buy a new 12.9-inch iPad Pro you won’t be able to use your existing Magic Keyboard—instead, you’d need to buy a new one. (Did Apple really not know how thick the 2021 iPad Pro would be when it released the Magic Keyboard for iPad Pro a year ago?)
It’s possible that the old case will actually work with the new iPads, but will fit awkwardly and might not close properly—since nobody’s gotten their hands on the iPad Pro yet. It’s one thing to have to buy a new case when you buy a new iPad, but at $349 the Magic Keyboard for 12.9-inch iPad Pro is a third of the price of the iPad itself.