Say the power law theory is predictive and that Bitcoin is here to stay for the long haul. The power law must break and turn into an exponential growth curve eventually, right?

Let's say BTC goes to $10 million or whatever by a few decades from now. The power law theory would have it become a much lower vol instrument in dollar terms with far lower expected forward returns against the dollar. Would it not eventually hit a point where it has expected forward returns of something like [GDP growth + fiat debasement + natural deflation] over the long run? I don't know how this works out, but something in the high single digits, perhaps? This would result in low exponential growth, not a continuously diminishing power law.