Er, maybe I was being unclear. Even if you discount a few specific scenarios, where do you get the strong evidence that no other technological existential risk with probability bigger than .001 will arise in the next hundred years, given that forecasters a century ago would have completely missed the existential risk from nuclear weapons?

I agree that cataloging near-earth objects is obviously worth a much bigger current investment than it has at present, but I think that an even bigger need exists for a well-funded group of scientists from various fields to consider such technological existential risks.