If one day most of countries in the world ban BTC, will someone with a lot of money spend million or even billion of dollars to establish a whole country. In this country, you will exchange with BTC and other crypto. Will you leave your coutry and move to this 'wonderland'?
There will be no someone who does it. The crypto currency will rule the whole country by it self. So there's no need to create a bitcoin wonderland. I believe someday in the future, you can use crypto currency everytime and everywhere. And its not easy to build a grand new country . Even if you've buy an Island, the Island are still belong to its government country.