If we want this, of course there is a big role from the government of each country that indeed must be able to provide a big rule in every country where they can legalize cryptocurrency as an investment.
Do you seriously think that governments are going to do that? They are not interested in people adopting cryptocurrencies since it goes against what they want, they want to have more and more control over you and they cannot have that control if you are using a currency that is independent of them, I am sure that in the future cryptocurrencies are going to be banned in many countries but as the economic situation worsens people will keep using them.