Euro banknotes.
Talk of Greece exiting the eurozone used to be impolite conversation. Now, market participants are talking about it like it's going to happen tomorrow. REUTERS

Up until the heady couple of days following the October 26 save-the-world summit, where European heads of state met in Brussels to discuss how to handle the deteriorating eurozone financial crisis, talk of a member state leaving the currency union was all but verboten. When the topic was discussed, it seemed mainly to be in the form of a Eurosceptic rant by a British politician or a salacious comment in a newspaper interview with some once influential, but now long out of the loop economist.

Back in those not so long-gone days, Swiss banking giant UBS issued a report suggesting a failure of the eurozone would lead to civil war. Economists concluded it just wouldn't happen. And former European Central Bank president Jean-Claude Trichet even once referred to such talk as an "absurd hypothesis."

Oh what a difference a month makes.

Since German Chancellor Angela Merkel and French President Nicolas Sarkozy gave an ultimatum to Greece at the beginning of November, suggesting that country could get kicked out of the European political and economic union if they didn't follow through with austerity measures, there's been a "seismic shift" in the way that exit scenario is being assessed.

Economists, especially those at financial institutions that would be hard hit by developments, are now openly talking about it as fait accompli.

"The endgame has begun and the ultimate outcome is clear," Rich Gordon, fixed income market strategist for Wells Fargo said in a video uploaded today to financial blog Wall Street Media, before predicting the upcoming exit by Greece from the eurozone.

Gordon's tone is not alarmist: in the same video, he predicts moderately positive U.S. GDP growth of 2.7 percent for the fourth quarter. But the fact Greece will have to abandon the euro seems as logical to him as a possible downgrade of France's credit rating, monetization of the debt by the European Central Bank and the establishment of "much tighter fiscal union, a much higher level of budget austerity."

Gordon is only the latest of the market movers to come out and say Greece will get booted off the union soon. Also on Thursday, Citigroup chief economist Willem Buiter wrote in a note to investors that a situation where Greece abandoned the euro would be "manageable." On Wednesday, a JP Morgan report put the likelihood of a euro break-up at 20 percent (not a forgone conclusion, but not an unthinkable scenario either) and noted corporate clients had already started buying derivatives to hedge against that occurrence. A day before that, Jim O'Neill, chairman of Goldman Sachs investment advisement arm said not only Greece "but maybe Portugal and in certain circumstances other countries as well" were on the chopping block.

British banks seem to have been especially prescient on the sentiment. In late November, as politicians in the U.K. warned banks to prepare for a break-up in the euro that the excitable British press was calling "Eurogeddon", a Barclays survey found that the number of investors who believed at least one nation would leave the eurozone had doubled since September.

Perhaps most astonishingly, sovereign central banks, including Greece's, are working under the assumption a Greek exit from the eurozone will happen. That kind of assumption has been floating since at least November 23, when the Greek Central Bank issued a blunt report that suggested abandoning the euro as a possibility.

Not everyone is convinced. Last week, two London-based economist for Japanese investment firm Nomura Securities issued a report saying Greece's exit from the euro would be "catastrophic" and that "no sensible" European leader would let it happen.

Furthermore, UBS, having predicted civil war, seems to have doubled down on its assessment, suggesting in a report Tuesday a euro break-up would rank up there with "the horrors of the first half of the 20th century."

Assessing what assets might make up the best portfolio in case of such a scenario, UBS head of global asset allocation Larry Hataway made the view that such an event would spell social chaos crystal clear.

"I suppose there might be some assets worthy of consideration -- precious metals, for example. But other metals would make wise investments, too. Among them tinned goods and small calibre weapons," Hataway quipped.