May be interesting to compare to smartphone adoption s-curve and the total population. Slope is likely to be similar from a technology adoption perspective. If you assume all fiat replaced then not sure 1M is enough.
In my application of the model, the population consists of all speculators who will ever buy bitcoins.
Problem is that speculators sell, and
adopters of washing machines didn't (c.f. the linked chart of technology adoptions over the past 100 years).
Wrong model.