What is money? It is a mechanism that can be used to facilitate exchanges of goods and services. It is nothing more and nothing less. That is true of all kinds of money.
When we think about crypto-currencies, we need to see them as a mechanism to facilitate such exchanges in those environments where existing facilitators (like banks and other middle men) do not operate: i.e., among those 3+ billion people who have no access to banks at all. If they are willing to use a digital currency to facilitate such exchanges, then crypto will be embraced by those communities.
At that point, fiat will compete against crypto and the chips will fall where they fall. Generally, revolutions seem to happen overnight but that isn't true. They happen at a tipping point that is only obvious in hindsight. So, let me ask you: if you focus on the need that crypto could serve in unserved environments, what do you think will be the tipping point in the competition between crypto and fiat?