If 90% of BTC are consumed by reserve demand and 50% of the global GDP is denominated in bitcoin, we will see $80mm/btc.
Yup. But that would be a very different world to the one we currently live in.
That's the idea ;-)
Seriously, Bitcoin has the potential to do much more than merely replace national currencies. It has the potential to allow dramatically increased world productivity and wealth. The financial sector is currently sucking off around 8% of global economic activity. Bitcoin could cut that in half.
There are more cars per capita now than there were horses per capita 150 years ago. This is because additional utility is produced at the margins. A more efficient disruptive technology can take more than 100% market share of the technology it replaces.
I was careful to be distinct about fiat inflation. Don't get me wrong - I think Bitcoin's epic and I'm a bit of a permabull too. But one bitcoin having the equivalent purchasing power of $80m of today's dollars within just five years just doesn't compute. It's just not feasible.