The planet can never die because of humans. The whole of nature is linked together and everything is connected and dependable on other things, and I mean everything. Also whatever exists in the planet is not created or destroyed, it merely changed form/energy and it will continue to do so. If and when people destroy all life, people will die also... and then the planet will simply "heal" itself, all of humans will rot and change energy into other forms, which will again just go back to the planet itself, and be used, reused and changed forms again over and over. The only thing that can destroy the planet is collision with other very large cosmic bodies, and if that happens it doesn't matter, it'll be very quick :) but even then people could by then figure out how to send people permanently into space, away from mother Earth.