Not 'when', but 'if'. This future is not likely to happen. At least, not with the current bitcoin's limitations.
The network capacity is just incomparable with visa and mc. Also, the constant price volatility is a huge stop-factor.
Crypto may take some part in the global economy, but it will not replace bank payments and fiat.
Just like the internet didn't replace usual mail as the means of transferring information.
Bitcoin doesn't need to grow scale wise to cater for every transaction on the planet. It's good enough as it is to act as a settlement network which would be in practice a better gold standard. So people would use second layer solutions like the Lightning Network instead of onchain transactions. This way even poor people in the end of the world could have access to the global economy, and this would be faster, cheaper and more private than any government alternative, so they have an incentive to support it.
At the same time, the elites have an incentive to support Bitcoin because they can afford on-chain transactions for their massive transactions and bypass the nation-states' controls.
In the end no matter what criticism you have about it, both rich and poor have incentives to support BTC, correct me if im wrong.