An agent is an amazing idea, and it would add enormous convenience - if implemented well.
But we're a long, long, long, long, long way away from agents. What we have now aren't even precursors to agents, more like very distant cousins to an ancestor.
In order to make what he's talking about, you'd need true general artificial intelligence operating at a human's level or above.
And if we have that, the entire world is going to change regardless - personal assistants will be insignificant in comparison.
It's difficult to predict when a breakthrough like that would happen, but I doubt it'll be within the next 200 years.
What we have now isn't even a stepping stone in the right direction, it's just smoke and mirrors that looks like it is if you only look at it on a surface level.