There are so many people employed in Numismatics. { http://en.wikipedia.org/wiki/Numismatics } and we also have many hobbyists, who collects coins.
When digital currencies take over from physical fiat currencies... {eventually they will... minting is just too expensive} ... What will these industries do?
How do they adapt?
There are other industries like this, who are going the same route ...example being the printing press... and Digital media.
It is kind of sad, to think about the legacy of these fiat currencies and what the new technology might be destroying.
Here is what I see happening:
They get filthy rich.
Why?
Because physical coins/currency will be a thing of the past, much like antiques or rare collectible items.
So their price will go sky high.