Given the fact that one "al qaeda" type person need only to fly one single 747 into one single spent fuel rod pool over in fukushima to kill off 3 billion people, and given the fact that there are, what, hundreds(?!), of these spent fuel rod pools all around the world, I think its safe to say that the vast majority of humanity will not be around in 400 years. Stupid monkeys... But as for computers? We're talking sub-cellular nanomachines with networked intelligence, probably even sentient. We cannot even measure today how powerful they will be.