It's always hard to predict the future because it hasn't happened yet. Let me give you an example in a similar industry: telecom.
Twenty years ago to this day, I was operating what was at that time the largest Internet telephony network in the world out of Toronto. We were selling international telephone minutes for pennies instead of dollars per minute, as the telephone companies were doing. When I travel now at night I'll often make a FaceTime video conference with my grandchildren. The marginal cost is zero. Over the course of 20 years we went from dollars per minute to a marginal cost of practically zero. The industry structure has changed tremendously. In fact, it didn't take 20 years to get there.
When you see a sea change of technology like this, things will happen very quickly. They will not change 2% a year for the next 50 years. You get to a point where, in a given environment, the new technology is cost-effective and it flips. We are approaching that point in many ways.
What is the time frame? I can't give you an exact number, but it will happen very quickly, given the trend that we've seen in the past, given the interest that we're seeing in the industry, given the amount of investment being made by all sorts of companies to make it happen.