The Euro like the dollar is just computer entries. They'll figure out how to create enough of them to keep things bumbling along. After all it's just a few key strokes.
But who regulates those key strokes?
The value, as for anything else is given by the demand and the offer.
If you offer more than the demand the price goes down, if you offer less the price (value) goes up.
What happens if the oil, weath, gas, is paid in Euros?
What happens if nobody wants dollars, or euros or whatever?
And what happens if with those key strokes you make something nobody wants?
Any prediction is going to be casual, because you cannot predict a future based on premises you do not know.
And in the same way you cannot regulate a market when you cannot regulate all variables.
There is only one way to do it: playing honestly, no tricks, no false money, no richness created with key strokes.
But that is hard and people do not want to be told sad stories.
They like to believe in miracles, they welcome the ones who promise all with little.
But arithmetics is a science, based on solid equations.
2+2 makes 4, but 2-4 makes -2.
Unless you make new rules (may be with a war), that -2 will always be -2.