At some point nations will have to prove their reserves and credit worth via BTC held, and so attract investment capital in FIAT or whatever.

Why? because the credit risk of a country with BTC will be much much lower and more transparent than any alternative.

Now that some of that BTC will be locked up in say a multisig, that will at least allow a lender to impinge on lenders total credit if they default.

Every other asset class can be destroyed, rigged, seized or sold and Legally if a country changes its laws.

Eventually countries will be forced to buy and hold BTC to remain attractive to investors and lenders as will business above a certain size to be good credit risks.

Banks or international banks or specialty benches such a sort of neo-Delaware Bench may arise and  find themselves in a new role or perhaps a  supra jurisdictional role as impartial arbiter of who get the funds in case of dispute. But then again perhaps not. It may be enough for a lender to demand multisig or more to give goods services etc

This I think will be the driver to 1M and above, when sovereign acquisition occurs in earnest and it will.


Notes:
I don't see that nations will ever trust each other enough to allow any single group of countries control the money supply.

Now I know the US$ is by far the reserve currency of the world, but by by and large this does not stop other major powers eg UK, UK, JP CNY trying to set their own internal monetary policy. Smaller counties may be dollarized due to being a the only viable alt to their devalued indigenous currency.

Putting that to one side I don't see the G20 and others ever trust each other enough and so will default to BTC.