Watching Survivor one can't help to wonder, "Could I do that? then the rabbit hole deepens.
We are endowed with the fate of CF. By God's work, our own choice, or random genetics we have this disorder. Nature and time conquer all. If a CF patient were to let nature take its course, I don't think this would necessarily be an act of suicide, but possibly recognition of fate, and a choice to not fight.
At any given moment we all choose to fight. How many times of taking up arms against this disease, before you are tired, exhausted? Perhaps you lost hope, the true currency of life for the impaired and challenged. Don't we all have the right to give in or give up, and not be a lesser person for the choice? If one has fought an honorable fight, having given one's best to triumph over or at best survive this disease, and at a point in time finds him/her self exhausted and without hope, I think that person can live as they die, with respect and dignity.
The true challenge of such a question is how difficult would it be not to fight? We all have ingrained in each of us a fighter's or warrior's spirit. Even when we want to give up, that spirit ignites our anger and carries us through our more difficult moments. How does a person, with such a warrior's spirit, relinquish the remaining strength he/she has to the choice not to fight? I am guessing most of us have been there or will be at some point. Would you choose, with your finite strength, to direct your last swing of the sword at your opponent, the disease, or would you choose to not direct your last bit of energy, but more choose to be, in the moment. Fighting takes energy, to exhale does not.
It ends up being a choice made by the individual. If let nature take it's course and live as my genetics will, I think -in my current status, I would expire in a matter of 3-4 months, depend on whether a cold or flu accelerated the process.