There's two usb slot in the back that can be for mic. Or the can make a wireless one that doesn't need to be connected to the Wii mote, like the scale. I also think there'll be one, or God save those voice chat zealot wii owners :x
oh...cuz wii needs to boost there online play. if they want to be successful in the online part of wii they have to get a mic or more action/shooters online.