World War III
Hasn't started yet. There are mounting regional conflicts:
- Ukraine vs. Russia
- Israel vs. Iran
- China vs. Taiwan
- US vs. China
However, I don't think that escalation in any of these theatres would necessarily result in WWIII. The probability of nuclear warfare seems minimal as well. Mutually Assured Destruction is just a theory that hasn't been tested in practice yet. If it does occur, it would likely occur between superpowers where neither side can win by conventional means.
Runaway artificial intelligence
Given that current generative pre-trained transformer models lack agency and general reasoning, I think that this is very unlikely to occur. This has been hyped up as a risk by people who profit from AI risk. Although AI is very likely to automate certain jobs out of existence, the economic impact is unlikely to be an existential threat to society.
6th extinction event
Extreme tail risk events which have a very low probability, but if they occur would be catastrophic.
- Nuclear winter: most deaths wouldn't occur from the initial blast, but from the destruction of habitat and radioactivity.
- Extra-terrestrials: it wouldn't even be a war, any space-faring civilization could easily extinguish life on Earth.
- Meteor impact: astronomically low chances of happening within a human lifetime.
- Ecosystem collapse: a point at which farming is no longer viable would result in mass deaths.
- Global pandemic: Bubonic plague levels of contagion and fatality, not COVID-19.
Prepperism
Most preppers are preparing for short-term civil unrest, under 3 months. It is very rare for civil society to just break down without continuity in government. Unless you live in a war zone, an adequate food and water supply is all that is needed.
Oddly enough, preppers are obsessed with guns, despite it being very low on the list of priorities. Community, food, water, medical supplies are far more important. In the USA at least, many civil unrest scenarios result in mass confiscation of firearms by the government. This is an indicator of conditions simply not being bad enough to not surrender.
Dissolution of government
This has happened countless times throughout history, most notable in recent history being the collapse of the Soviet Union. What was surprising was how swiftly it had occurred, and how few people expected it.
I think that this is most likely to happen to a few states: USA, Israel, various EU countries, South Korea, and Japan. USA may reach a constitutional crisis in which its founding documents are discarded and rewritten. Israel will lose militarily to its neighbors without foreign support. European countries may be overrun by foreign populations and thus they will be governed by their new rulers. South Korea and Japan are currently vassal states to the USA and may re-declare independence in the future.
Due to the vast majority of governments having a monopoly on violence, dissolution of government is very unlikely to happen via revolution or (para)military action, but rather they will collapse internally via demoralization. "They pretend to pay us, so we pretend to work."
Anarcho-tyranny
When a failed state does not collapse, the default state is anarcho-tyranny. The state is unable or unwilling to prosecute actual criminals, while regular citizens are incarcerated for trivial infractions of law. Whether it is by incompetence or malice, the state does not need to exert much force to terrorize its citizens and enables criminal behavior to achieve the same effect, sometimes via corruption.
This is often referred to as a two-tier judicial system, but in fact laws have been selectively applied throughout history. What also happens under anarcho-tyranny is lawfare against political opponents, such as NKVD troika.
Population collapse
This is already happening, although the timescale at which it is happening is much longer than anyone really notices. The lowest birth rate in the world goes to South Korea, at 0.68 children per woman.
The larger issue is that this is a global phenomena, when a country escapes poverty conditions and modernizes, fertility rates almost universally decrease. More economic opportunities for women is correlated to less women having children.
Economic meltdown
This seems highly probable. I think that one country that has it overdue is the USA, sovereign debt is what will cause the federal government to crumble.
In this scenario, there would be hyper-inflation in which the currency is debased to be worth effectively zero. Bartering assets would be the main economic activity, and it would likely be exchanging precious metals or crypto-currencies. The government may issue a repeat of Executive Order 6102 in which gold is confiscated, or issue draconian laws regulating crypto-currency exchanges, which they are already set on doing.