Briefly, from where I sit, the best possible result is the collapse of the European Union as both a political and an economic entity.
The attempt to meld together in a single polity, welded together by bureaucracy and socialism, the nations of what is (for the moment) the European Union was doomed from the start by the and differing conditions/languages/cultures/economic realities of the member nations and the long-established rivalries and hostilities amongst them.
And those nations, each of them, have much worth preserving among them free from the deadening hand of supra-national regulation.
Trying to force something over a double dozen randomly polygonal pegs of varying size simultaneously into a single rather smallish round hole is not a project with good odds of success.
For the stability of Europe, and of the European and word economy in the long term, devolving back to national currencies and national economic planning and regulation offers the benefit of allowing for failure - if one sovereign nation fails (or even several) fiscally, it is unlikely to take others with it. In the current system, it appears that the EU is a mutual economic suicide pact.
As a bonus, national borders and sovereign nations allow individuals - when political or social conditions become to oppressive (or the stupidity level rises beyond tolerance) - some place to go TO.
Again, from where I sit, there will be rough times and a difficult transition back to sanity - but the day the EU falls is a day all of us, world wide, should celebrate.