Basically, I think what we're seeing is the core on the new controller.
Something simple and sleek to attract those non-gamers Nintendo has been clamoring for. But I do think there will be a standard controller that attaches to it. Nintendo probably didn't show it for two reasons. The first being that it wanted to focus on the new technology the controller would allow. The second being that they haven't completely decided what it will look like yet. If you think about it, this really makes sense. Having the motion detection simply implemented into a normal controller would completely destroy Nintendo's goal of attracting non-gamers and games that rely heavily or even entirely on the motion detection would be hampered by a dozen or so buttons and analog sticks. I speculate the system will come standard with the core remote, the corded analog stick, a standard controller that will firmly attach to the core, and a mic. Different combinations of these accessories and future accessories (touch pad, etc..) will allow for a multitude of unique game styles as well as ALL traditional ones. Many of those traditional games will actually be exponentially better with the new motion detection in addition to the standard buttons.
I believe that while some multi-platform games may lazily rely on the standard controller accessory, many games will actually be tweaked to work the core controller. If you think about, just about everythink the standard buttons and analog sticks have done in games these past generations could be adapted to the motion sensing techlogy. I think as more developers come to utilize the technology, we could eventually see the standard interface become truly obsolete. It would simply be a mistake for Nintendo to retire it before developers are ready to let go of it.