You did say "replace small slabs of glass that we look at and touch", so I think "voice-only" was a reasonable interpretation.
As I said, I'm all for trying new stuff. We should look at the extent to which computers can usefully leverage that channel. But I don't think we should presume that it will be particularly useful.
My point is that voice is a powerful and ancient channel, and it's about time that computers leverage that channel.