The way I see it, the collapse of governments and the lack of new ones, even if none of the above scenarios happen, will lead to the inevitable end of the Earth. My reasons being:
1)
The degrading of Terra: No governments, nothing to keep nature from the greedy hands of humans. Wildlife hunted for food. Vegetation can be completely snatched from all over the world. Pollution goes untreated. And there are fires to worry about (in case your wondering why would people burn forests, let's remember the state of chaos here. Also fire can start in the wild for no apparent reason). Sure, there will be people trying to protect nature, but how long will they last, and how great will their impact be? Over time, the Earth will be totally wrecked by pollution and deforestation, and its greatest and most destructive inhabitants will succumb to their own unsatisfied physical needs.
2)
The mutual assured destruction of Terrans: There's always the chaos caused by
lovable criminals and psychopaths now that there's no major organization containing and fighting against them. The battle against crime will become that of an equal battle, where the more numerous but less experienced and widely unarmed civilians must face their less numerous but ruthless, experienced, barbaric and more well-armed counterparts, with communities no bigger than a small town against organized groups of evildoers and stealthy individuals out for their properties, precious supplies and lives. The result being civilians and bandits alike die because of the conflicts and famine, lots of bandits survive and further destroy the nature and civilians forced to resort to taking necessities from the wild. Speeds up 1) and lowers population.
3)
The self destruction of Terrans: Let's try to picture this. All of your wife(s), aunts, uncles, father(s), mother(s), grandparents, children, siblings, etc. all die of some terrible cause. The leader of the town is being complete BS. Some petty thieves visited your house and took all your food, water, batteries, ammunition, weaponry, CDs and game consoles. They only left you with whatever furniture they couldn't carry, and a one-fifth loaded Taurus Raging Bull. No matter how tenacious you are, no doubt you'll consider for at least half a second to use that last bullet to end all this dipshit. Now imagine that most of the world's population are in a same or similar state, even among the bandits. There will be extravagant mass suicides, civil war within towns and gangs everywhere. All the chaos helps a lot to fuel all of the destructive measures mentioned in 1), 2) and 3).
4) Mass Chaos + Shitloads of Deaths + Fucked up planet + Psychology stress = Gradual Inevitable Total Annihilation. GITA. Pronounced GUITAR.
Me? I'll lock myself in some biolab and work recklessly until I am able to create a zombie virus, go infect lots of people with it, THEN grab my semi handgun, The Zombie Survival Guide, The Zombie Combat Manual and survive and be glad that I've at least slowed down the GITA of Terra by sacrifice a little bit shitload of Terrans.
None.