15 years? I really, really doubt. As advanced as medicine is becoming, CF itself isn't homogenous enough that a "cure" for it could be easily available.
I can see some aspects of the disease being effectively "cured" by then (or soon after). Improved genetic screening could help ensure healthy kids are born, instead of ill ones. Advances in lung transplants, and overhauls of the donation system, could fix the organ shortages and make it a much easier surgery for those facing late-stage pulmonary complications. Vaccines for pseudomonas and cepacia could be fine-tuned, and we've seen how people without those bugs tend to have life expectancies comparatively sky-high.
Speaking of a "cure for CF" is way too simplistic, I believe, given how diverse its array of symptoms is, and how many stages it goes through. Correcting the deficient gene would "cure" everybody who isn't already sick, but do next to nothing for those whose lungs are FUBAR. Perfecting transplant would "cure" late-stage CF, but do nothing for those earlier on in the disease. And both of those could leave the other side effects of illness, like liver problems, need for digestive enzymes, etc.