Squilliam,
I think your comparison to a typewriter works for a device like an ebook reader; which is a very static, single purpose device and its primary benefits will be (eventually) matched or exceeded by low cost portable devices in the future.
The biggest strength a dedicated gaming device (console or handheld) has over a generic computing machine (PC or portable device) is what I would term Agility; which could be defined as the ability to radically redefine your position within the market to create new gaming experiences.
In much the same way as the user interface of a PC hasn’t changed significantly since Microsoft “got it right” with Windows 95, in 10 to 15 years the way people interface with their smart-phones or tablet PCs will be remarkably similar to how people use them today.
In a similar way to how Playstation Move, Kinect, the WiiMote, dual screen & touch screen gaming, analogue & hidden butons, analogue & dual analogue sticks, shoulder buttons, and the D-Pad have been involved in the steady evolution of user interfaces on dedicated gaming devices over the years, Nintendo will be able to steadily evolve the user interface of their handheld systems to offer a different (and arguably better) than what can be produced on a generic portable computing device.
