It depends on if it provides the utility people need. If that were to happen people would have to evaluate whether they'd get more utility out of their national currency or the alternative. If the national currency loses 50% of its value but they can still use it to buy things, they'll probably stick with that. An alternative value-store doesn't serve the utility need if no one will accept it. So the focus should be on providing utility to customers.
The main use will be preservation of capital, not alternative spending power.
If the whole world goes down at once, (as it might) then there may or may not be any utility.
(Receipts for gallons of gas served as currency in Argentina a couple of decades ago, for example, so it could be a Godsend if the network stays up.)
But as a minimum, serving as a way to teleport out of the way if the dominoes start falling one by one, oh, yeah... as long as there are off ramps many dominoes further down stream.
:)
(http://geekologie.com/2013/11/13/domino-tricks.jpg)