I don't think each controller will have a 6" touchscreen. I think one 6" tablet will be included with each system. The tablet will have a stand, and it's designed to sit on your coffee table. The camera will be on a swivel, so that it can be used for video chatting, AR, and possibly biometrics (retina/pupil). It has built in IR (or new motion sensing tech) that allows you to interact with it via the Wiimote.
Seamless inventory management, constant display of secondary information, and easy access to OS features would be strong points of the coffee-table tablet.
The biometrics portion is particularly interesting, especially if the tablet includes both a pulse oximeter and retinal / pupil detection.. Those are the exact two biometric features that Gabe @ Valve mentioned regarding the new generation of consoles.
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I also think there is a decent chance that the screen will be 3D. Iwata talked about including a 3D screen with the Gamecube, but it was cost prohibitive at the time. Perhaps this is the other surprise to be unveiled at E3.
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