I expect Nintendo to have some kind of chat in the future, most likely it would be a mic accessory. I think the reason we haven't seen it yet is to avoid the ESRB T rating that automatically goes onto internet games.
As we start seeing games that are already rated T like Soul Calibur and probably SSBB we'll probably see a chat function.
Blue tooth would be better though, I don't want my headset to be attached to my flailing arm. Either It'll fall off when I need it most, or the wire will be so long it'll become annoying.