That mock-up at least maintains the functionality of the Wiimote, which Nintendo would be mad to throw away.
But would you let your kids wave that around?
Expense, fragility, battery life. All the current rumours are at odds with 3 things that are the basics of controller design. Something Nintendo has always been very careful with. Until someone comes up with a compelling and feasible reason why a 6" screen is in there, it just doesn't ring true no matter how many ways we try to make it fit.
And making the screen separate is just bundling an expensive extra which won't be used by everyone, and takes the focus away from the TV which should be the focus of your new HD console.
Gah, need more (preferably real) info.