We are already on a Bitcoin Standard.
Hold/save in the best available and spend the inferior local currency when needed.
No need for 100% adoption for everything to work just fine.
Bitcoin is already the world reserve currency.
I have some local US Dollar Currency on hand to buy my everyday walking around items.
I did the same thing when visiting Mexico in years past. I kept my long-term assets and savings all in US Dollars but exchanged my US Dollars for Pesos for walking around money.
I do the same thing now in my home state of Colorado... My Bitcoin is the standard and my local US Dollar Currency is the inferior currency I use to spend around town around.
No need for 100% Bitcoin adoption to get to this point.
Bitcoin is the financial equivalent to the marine navigation concept of dead reckoning.
In marine navigation, dead reckoning is the process of calculating the current position of a moving object by using a previously determined position, or fix, and incorporating estimates of speed, heading (or direction or course), and elapsed time.