The end of the world is not coming any time soon. What the hell kind of bullshit is in that first post? "Masters of the System"? I'm sorry, I wasn't aware that the Sith Emperor was in charge of our world. How in the hell can the ENTIRE FUCKING WORLD get wiped out by an earthquake or flood? Believe it or not, this is not the bible where god can send a great flood to sweep the world clean of people. This is a world where a flood is caused by heavy rain, tsunami, hurricane, or dam breakages. None of these things can ever happen at a global scale. Ever. An "earthquake at a scale we have never experienced?" In all of the geologic history of this planet, there is no evidence of an earthquake large enough to wipe out the world. Not even close.
Disease spreading through the entire human population enough so that we cannot maintain a viable gene pool? Please, cut the fear mongering crap. I'll run some numbers for you since science is rather lacking in threads like these. The ebloa virus, one of the single nastiest viruses in the world, has a mortality rate of 50-89%. There is no known cure for it. However, it does not have the capability to become a global pandemic; its high mortality rate and rapid incubation period cause it to burn itself out within a short period of time, without spreading too far. Any government quarantine on a disease like this is enough to stop an outbreak.
Even the nastiest of pandemics, something like a SARS or an antibiotic-resistant tuberculosis, lack the ability to "end the world" by the definition of what allows them to become a pandemic; that they have a long incubation period (the virus that causes TB can remain dormant in the body for years, but only 5-10% of people carrying the virus will actually sicken and become infectious), and a relatively low mortality rate. Even something like the Black Plague, which wiped out 70% of Europe's population, had a relatively small mark on humanity's history when it still left 350 million people alive out of the 450 million that were originally living in the world. Hardly a world-ending event.
I have no idea whether or not there is a theoretical population ceiling that this planet can support. But I do know that humanity will try its hardest to break that, and continue on growing. We have made a point of surviving, its something we do very well and will continue to do for the foreseeable future.
If you actually read this post, I hope you are a bit smarter now because of it. If you haven't fuck you go learn something before you go preaching that "The end is nigh".