I am looking for a study I found a couple years ago that stated what percentage of people with CF have bronchiectasis by 18 yrs of age. I think remember it being 90%, but I cannot find the darned study. I do believe it was based on high res CT scan, which detects much milder bronchiectasis than x-ray.
In the meantime, here is a very interesting study/collection of data that almost gives the answer to your question.
Notes for example, that by age 15-16 years, more than 60% of patients with CF acquire a P aeruginosa infection.
<a target=_blank class=ftalternatingbarlinklarge href="http://emedicine.medscape.com/article/354931-overview">http://emedicine.medscape.com/article/354931-overview</a>