Sorry, but you are wrong here. Let me explain:
Let's say the euro-zone does indeed weaken and nobody wants to hold euros (outside of the eurozone members).
When Germany sells something to say the US, they will get dollars. These dollars are reserves for Germany. With a weakening euro those dollars are then worth more. So if a worker was to get a 100 euros for their labors then at some later point in time those 100 euros will be worth less dollars. Thus Germany has higher reserves.
The key here is that it is not about the Euro, but about the ability of the eurozone countries being able to build up reserves in other currencies. This is why Japan and China can do what they want. They have huge reserves in currencies other than their own. Thus when a company within the country needs to purchase with a hard currency they can do so with the reserves.
You say that the dollar cannot recover. The reality is that it is recovering because people think the USD is the reserve currency of the world. Thus whether the US likes it or not their value will go up. Of course when people actually decide to dump USD it will not be pretty.
The currencies becoming trash is not completely correct. What will happen is that the EUR, and USD will devalue themselves with respect to the REAL, CAD, and other currencies. The currency advantage that the emerging countries had before will evaporate.
This is a good thing because it means emerging will no longer be emerging. We are leveling the playing fields and that is good... Of course those who live in EUR, USD, and GBP land will have to make do with less.
If I were young I would have left EUR, USD, and GBP land...