I like how this is a poll, like it's all a matter of opinion.
Anyways, the world will probably end in about 4.6 billion years, when the sun transforms into a red giant, possibly getting big enough to engulf the earth in a cloud of cosmic gas around 5000 K in temperature, or possibly sending the earth into a radically different orbit, killing of all life as we then know it because of a global and drastic change in climate. (not like the ice caps melting, more like them evaporating, or the temperature dropping to -100 degrees Celsius average)