The Dawn of Gestural Computing
When the device was only a glass rectangle we got touch computing. When that surface is variable and multi-modal, we arrive at gestural computing.
Bringing this to market required solving mechanical and UI problems but also conceptual, jobs-to-be-done questions. Perhaps more productivity, perhaps more creativity. The folding mechanism is a wonder, the surface treatment is chemistry and noting also the liquid glass application, the new interface is magical. These developments, and, undoubtedly, more to come, were necessary to make the idea of gestural computing not just possible but attractive.
Now a new gesture language will emerge: Opening, closing, propping, typing, flipping are all new, adding to swiping, rotating, pinch and zooming brought to us by multi-touch. The promotional videos Apple released highlight these new gestures visually presenting the product as not just being a 2D slate.
Naturally, the folding capability will come to other screens in the Apple pantheon: the iPad, Mac, and a multitude of iPhone sizes. Missing elements will be added back to the Duos: FaceID, spatial photography, top-level cameras. The Duo will stand next to it first but eventually will likely eclipse the Uno.
A foldable screen introduces a new gesture language: opening, closing, propping, typing, and flipping.