I can definately see the benefits of samsungs folded variants versus a tablet or ordinary slab. And clearly using half for a fake keyboard is likely to work much better with android than a fake keyboard on a slab.
But that said I see two drawbacks. Primarily that it isn't a keyboard with real keys, and secondary that the surface will be prone for scratches, as we can not have both hard and bendable with currently known materials.
So I see it as the optimal device for those that do some typing and still also want a large screen for other stuff. But not ideal for those that do a lot of