As far as I can tell, there's no reason to believe fiat currencies/economies are headed for any kind of collapse.
Sure there is: the simple mathematical fact that an ever-increasing expansion of debt (which the current system is based on) is unsustainable.
Debt is just a number, a value stored in a computer database. A number can get as big as you want it to get. If you were talking about exponential growth in the use of resources or energy, etc, I'd agree, that's mathematically not possible to sustain forever. But if we're just talking about currency/debt, the numbers can just as easily be quadrillions as billions, can just as easily be 10^100000 instead of quadrillions, and society will look no different.
The number used to enumerate the debt is directly related to usage of resource or energy. It represents deficits in both items.
So, it's not "just a number" at all. It is a symbolic representation of how much resources are used by a particular process. If the numbers don't all add up then society's goals and the means to legitimately attain them will not correspond, a condition called "anomie", which is exactly what our society is currently facing.
Colloquially when people talk about how society is "breaking down", or the family unit is "breaking down" they are referring to this sociological process. People begin to ignore social norms when they figure out they are useless, or worse, detrimental to their own individual interests and thus "society breaks down". Right now it's just people being a littler ruder or ignoring social conventions. But if it gets bad enough even the most deeply ingrained social taboos such as the prohibition against cannibalism, and the social evolution that caused humans to stop looking at each other as a food source could be erased, just like that.
If you can't see how this relates to the social situation in the developing world you have your head in the sand.
The cost of energy or resources in units of fiat currency changes. We have inflation, etc. Just because there's 2% more currency this year than last year doesn't mean there's also 2% more resources in play... there are many other dynamic factors involved.
In regards to society "breaking down"... people always say this, but there's no evidence of it actually happening. In fact, crimes of almost all kinds are at their lowest in decades in many Western countries. And as for the developing world, wealth is being rapidly created there and a new worldwide middle class of hundreds of millions of people is rapidly emerging.
We are living in the golden age of humankind.