"In terms of the voice recognition, that has been progressing steadily for 30 years too, and I imagine Siri will benefit from improvements to the technology base, as others will"

Will it progress to a point where ambiguity is reduced to nil? The strength of the command line abstraction is its completely unambiguous interface - do what I say.

The do what I mean interface of Siri could be limited to actions with insignificant consequences - the human brain incorporates the best speech recognition available and still makes mistakes. Any speech AI performing significant actions would need to outperform the brain.

edit: That is not to suggest AI speech recognition outperforming the brain is not possible. There are probably metrics and methods for disambiguating common sources of confusion which could be performed in the blink of an eye rather than the minutes, hours or weeks later you find yourself thinking "Oh, THAT'S what he said!"