What kind of reasoning leads you to this time estimate? Hundreds of years is an awfully long time

Humans are notoriously poor at providing estimates of probability, and our ability to accurately predict scales that are less than immediate are just as poor. It seems likely that this "hundreds of years" was a short-hand for "there does not seem to be a direct roadmap to achieving this goal from where we currently are, and therefore I must assign an arbitrarily distant point into the future as its most-likely-to-be-achieved date."

This is purely guesswork / projection on my part, however.