It would be nice if you’d have laid out some of your reasons for having such a high belief in this. I’m not so sure it’ll ever happen. My personal beliefs are that it’ll always be a sidekick in some sort of way to fiat currency for some time until it takes a turn and gets over some major flaws/issues like expense , transaction totals and speed, which are taking time to build.
In the same way that every country currently uses their own currency locally, and trade internationally with USD, countries will continue to use their own currencies, but slowly over time more and more countries, specially poor ones, will start to realize that they don't have to use USD to send money internationally(Remittances) paying huge fees through companies like Western Union.
Instead, those countries will start using Bitcoin, with almost no fees, and no need to go to any third party and ask permission. With the popularity of working from home increasing, globalization continuing to expand, and technology becoming pervasive, it is just a matter of time until these countries realize how much money they can save if they use Bitcoin instead of USD.
Those countries will probably be the first layer upon which Bitcoin will establish itself as the new global currency.
At the same time, new applications like Strike for example, will start allowing richer countries to send money overseas with minimum fees by converting local currency to Bitcoin, making a Bitcoin transaction (instantaneous and almost free), and then converting it back to the other country local currency. This is already starting to happen. In the future there will be more countries adopting this, and more companies doing similar things.
This all leads to an ever increasing usage of Bitcoin for international trade. It's just better in every way compared to the legacy financial system. Faster, freer, cheaper, and accessible to anyone.
In a couple of decades it will be so pervasive that people will wonder how we even send money overseas back then.