I agree that the adoption rate will be slower than the 3-5 years rate stated by the commenter above.
I do think, though, that of the major cities, many people would agree that Chicago is among the most resistant to changes in labor due to customer preferences, due to its unique political system.
That said, though, imagine how absurd it would have been 6 years ago to imagine the market share that the Chicago yellow cab companies are losing, to newcomers that didn't even exist yet. I don't think many people, especially cab companies and Chicago legislators, could have predicted it.
The swell of opposition in legislators against cheaper technological answers to current labor solutions is heroic- the question that remains is, 'How long before consumer demand for the radically cheaper and/or more efficient option makes the opposition moot?'.
The answer usually seems to be: 'Sooner than everyone thinks.'