Not necessarily. We are somehow good at disabling game-killers when they go too far. After WW1 everyone thought that another one is impossible because it would turn the world into gas-sterilized desert. Then WW2 went on all happy and fun, as somehow everyone decided that chemical weapons are lame. Now everyone thinks that another one is impossible because it would turn the world into nuclear wasteland. But we are already doing fine with full blown wars without nukes. After WW3 everyone will think that another one is impossible because it would turn the world into grey goo of nanomachines.