In about 5 billion years the sun will become a red giant and engulf all the planets up to about Mars. You don't have anything to worry about, though, just don't search for immortality or anything like that
everyone will die eventualy, so even if humanity ends (and it most likely will) it wont matter as much as you may think, for example if humans found a way to live forever, well what if they eventualy learned so much over time, this may cause people to become bored because there is not anything else to learn and no where to travel. then we humanity would be doomed to an eternity of boredom
well according to the aincent mayans the world will end on december 27, 2012 (im not sure if i got the day exactly right), they actuly had a calendar of the future, and it ended on that date
People have been predicting the end of the world since the first calendars were developed. The idea that some intelligent external force will destroy the world implies a lot of things that don't make sense.