What will they plug into the Wiimote next?

[Grey Acumen]

supposedly, you could connect more, but honestly, it's hard enough making sure those various connections all hook up properly, plus, it's hard to decide if the first microphone is the first player's or the second players if you're doing it all wirelessly. When the connection is physical, the system automatically knows that everything being sent on this signal is player 1 and everything on teh other signal is player 2, etc.