The Nintendo rep that was at my event yesterday said that Nunchuk support was still a possibility.
As for 3D support, I'm doubting the hardware chosen for the Wii U could support it if they wanted to, so I don't see that coming. This gets down to the same reason the Wii wasn't an HD console. Nintendo felt that the install rate of HD sets weren't high enough to warrant it. While they didn't forsee it increase as greatly as it did in the next few years, 3D TV install rate is still very small and I don't see it spiking the way that HD sets did from 2007-2010.