This should help illustrate why I think it will start to happen within 40 years:
The Age of Spiritual Machines - Wikipedia, the free encyclopedia
And remember, virtually all of Kurzweil's predictions came true. He predicted CI's will be widely used in 2019 but I think he's predicting that too late. It already is.
He predicts that books, audio, and videos will be all digital downloads.. it's already happening. He predicts war to be mostly unmanned and it's happening with our drones. He predicts online learning... already happening... predicts text generation with speech recognition... we got Google to put captions... it only gets better over time.
And here's the thing... by 2020, a $1000 personal computer will have as much power processing as a human brain! He predicts that cars will be automated and it will happen with Google's experimental self-driving cars that prove to be extremely accurate and so far, when unmanned, no accidents.
He predicts that nanotechnology will become practical by 2019 but I think it will happen sooner.
Remember, it was just 10 years ago when it took 36 months (three years) to decode human genome costing millions of dollars. Now it can be done with less than 50,000 dollars. And in 5 years, it should be just $500.