The world, in terms of Earth being habitable for complex life, is predicted by scientists to end in about one billion years. This is due to the sun's aging and gradual increase in heat, which will warm the Earth's surface, cause water to evaporate, disrupt the carbon cycle, and ultimately lead to the collapse of the oxygenated atmosphere necessary for most life forms today. Eventually, this will create an unlivable environment for oxygen-dependent life, though simpler microbial life might persist longer. The Earth itself will likely be physically destroyed or rendered completely uninhabitable around 5 to 7.6 billion years from now when the sun becomes a red giant and possibly engulfs the planet.
Various cultural and religious predictions exist, but scientifically, the most definitive timeline relates to astronomical and atmospheric factors governed by solar evolution.
In short, the Earth will not "end" anytime soon from a human perspective, but in a very long-term future measure — about one billion years from now for complex life and several billion more for the planet itself.
