To the OP, it doesn't seem as if anything drastic will happen within a day anyway - because I highly doubt a country as entrenched in the european integration project as Germany would (or even could) withdraw;
There has been so much work put into the EU and the EC (both political and economic union) that I highly doubt that it would disintegrate as quickly as has been suggested here. Numerous political careers across Europe have been staked on the success of the project. Germany's withdrawal would effectively mean the end of Merkel's career and probably a massive hit for her CDU party. Sarkozy and the UMP would also take a massive hit - remember, Chirac disregarded the no vote in 2005 for the EU referendum, the public has been dragged along kicking and screaming.
I suspect their initial efforts will be focused on finding ways of patching up the debt crisis so that the status quo politically is as unchanged as possible. So my thought is that this crisis may foster to create even more political control of euro member economies - although not in a way that increases public accountability.
In the future, I think we'll see the ECB dictating budget limitations to euro member countries - which will not be politically palatable to the voting public, but I do think will drive forward political integration.
Something's got to give alright - it's going to be the tax-paying public, and noone else. Paying down the debt and closing the deficit will come out of their, and only their, pockets. We'll see more of the austerity riots, for sure, and new political movements, to be sure. But the beast is already out, and I think an integrated europe is more of an inevitability given the control banks have over the economy and bureaucrats have over the political process.
This is only one of the three functions of currency. The idea is that coins are made flat to stack, round to pass around, and have numbers on then so they can be counted.
Swapping value - passing money around - is just one function of a currency, and for this one function a single currency would work well.
Storing value - stacking money - can be done by a gold standard (indeed the old idea of the gold standard system in effect tried just this, with national currencies acting as promisory notes for a quantity of gold). But once you leave the gold standard the currencies are backed by the strength of the economies of the nations. The value of the pound in your pocket depends on the value of the UK economy. A single currency as store of value works if all the nations have an economy of the same strength, and economies strengthen or weaken at the same rate. It cannot work on an average of the strengths and weaknesses of several economies.
Counting value means that that no country makes the count go wrong by printing money.
A currency will work only over the geogrpahical area where these three criteria are met. For a currency to work you must have a full fiscal union with a single point for issue of bonds. You have to have economies which are relatively similar in a full fiscal and political union.
A world currency would only work with a world government and a world economy. Currency unions are enormously problematic, and either break down or lead to full political and economic union (the process can take as long as a couple of decades). The introduction of the euro absolutely required full fiscal and political union to make it work. We don't have that, and even the most ardent Europhiles cannot imagine getting full fiscal and political union in the next few months. Economics 101 says that the euro must fail. Greenspan has made a point so obvious that it should hardly need saying, and every banker and economist knows it. The pity is the politicians don't seem to believe it. Really it should be Greece that leaves, but the political and legal knots are too ghastly. So we have to start the unravelling at the other end - Germany has to leave.
