You know how in Minecraft there is a point where you can't advance any further?
Like when you get diamond everything and beat the Enderdragon. That is endgame in a sandbox type game. What do you think will happen when Humans reach a state of endgame? We've figured out the periodic table so new stuff like magic transportation crystals aren't gonna pop out one day. When we figure out how to mass produce nuclear energy, then what next? In Minecraft you can install mods like Equivalent Exchange or Buildcraft. You have loads of new stuff then, but not in the real world.
Maybe we will kill ourselves off, or maybe we will live to see the sun blow up, who knows?
Just a thought that occurred when I was watching my quarry do all my work for me in Minecraft.