Might it be that a 49 year old develop cystic fibrosis?

Unlikely: At age 49, a diagnosis of cystic fibrosis would be very unlikely. That being said, a diagnosis of pulmonary fibrosis, which is different from cf, could be possible, and generally occurs later in life. Pulmonary fibrosis can give the same signs and symptoms as cf. You can experience shortness of breath, cough, fatigue, and weight loss. Smoking is a risk factor.

Yes: Mild variants of cystic fibrosis pop up at any age. I autopsied a case that was missed in a woman in her 70's because her doctors didn't consider it. Chopin's illness was probably cystic fibrosis.