If you mean bitcoin to be a global currency that can be used by all people in this world and used as a payment system in various aspects, it is impossible to happen with confidence for many reasons. Only people are crazy about bitcoin and have a passion for bitcoin to have a high price that wants it to happen.

But if you mean bitcoin become a global currency only for people who know bitcoin, for instance, I live with you in different country and I will sell the goods to you and we have agreed the payment instrument that we use is bitcoin, indirectly bitcoin has become a global currency. Because we have a different currency, but with bitcoin everyone who uses it is the same.