It's inconsistent to expect the future to be better than one expects. If you think your probability estimates are too pessimistic adjust them until you don't know whether they are too optimistic or too pessimistic. No one stops you from assigning probability mass to outcomes like "technological solution that does away with problem X" or "scientific insight that makes the question moot". Claimed knowledge that the best possible probability estimate is biased in a particular direction cannot possibly ever be correct.