HCI will stay visual People find it difficult to think and speak at the same time. Therefore, controlling computers through vocal commands is too mentally taxing to be useful--better to stick with hand-eye coordination.

I think Don Norman put it most clearly when he said speech interfaces were no panacea to complex computing. The biggest problem with speech programs currently is that they poorly transcribe what you say. But if you use a keyboard and type the information in, transcription is perfect AND this doesn't help make the machine any easier to use. The only thing that will do that is watching how people actually use machines "in the wild" and then design directly off human behavior.