I'm sorry for poor phrasing, what I meant to say was that at the time of WWDC, iOS 5 adoption of the population at large was 80%.
iOS 6 is still in beta, it will probably be out to general public sometime this month.
Right - I recall reading an article/blog/comment/pundit (Gruber? Marco?) that suggested that their were was a greater percentage of people using IOS 6 than there were Jellybean in the general population, right around the time of WWDC. At WWDC proper - I would expect a sizable percentage of developers were running IOS 6 on their devices.