It's definitely too early to think about it. If the colonization of Mars occurs relatively soon, then various equipment from Earth will be supplied there for a long time. In this way, money can also be supplied. And what will happen later, no one knows yet. Also, no one knows what awaits the cryptocurrency even in a few decades. In any case, this is not a problem of current generations. In the future, with the gradual exploration of outer space, a more valuable material than gold may appear, and it is he who can become a universal means of payment.