Do you have a reference for that? My copy of Our Final Hour contains the same sentence minus "without a serious setback".
Our Final Century, page 8 line 4.
It seems as though Rees - rather confusingly - said different things on the topic in Our Final Century and Our Final Hour.
http://vimeo.com/22099396
What do people think of this, from a Bayesian perspective?
It is a talk given to the Oxford Transhumanists. Their previous speaker was Eliezer Yudkowsky. Audio version and past talks here: http://groupspaces.com/oxfordtranshumanists/pages/past-talks