I don't really see the point of looking so far into the future when it comes to Bitcoin. There is no real reason to believe that Bitcoin will take over as the world currency, nor that it will even maintain its success so far into the future. The need for currency becomes pretty much nil when everybody has machines that can literally rearrange atoms into whatever they want. That is the truth of the distant future, nanoscale micro-assemblers, the end of patents, the end of currency, the end of trade entirely.