Nintendo (Iwata, I think it was) shrugged off a mike when questioned about it. He didn't say they wouldn't include one, but he did note that including a mike wouldn't be any big deal/secret/revolutionary feature.
Oh, and curse this split discussion. As I said in the other thread, I think there's a good possibiliuty that one of the hidden features of the controller will be the ability to download games to it, and the ability to plug it directly into a tv to play.