There are many people who are treated as if they have CF but unconfirmed genes. If you really want to hear from them, try posting in the adult section with a descriptive title about what you want - you may draw a few of them out to respond.
Knowing the genes is helpful but not necessary for all the normal treatment options that are currently available. His care will not change because they do not know his gene mutations yet. You may just want to run a genetic test every 5 years or so to see if they have identified anything yet.
To the best of my knowledge there is only one treatment option coming down the pipeline for those with an X in their gene type. I don't remember the specifics but I do know whatever drug it was would only work for those with that type of gene defect. But again, that has absolutely no bearing on his daily treatment or how the doctor will choose to handle his symptoms or preventative/maintenance care for now, because that drug is not even finished with testing yet and for the larger majority of people with CF, it will not be an option to use.
I'm glad to hear that they are willing to treat him as if he has CF -- this will insure he gets the best care. Having him followed by a CF doctor, attending clinic visits every three months and starting treatments will greatly benefit him not only now but in the long term as well. I'd have to stay that getting proper treatment is far more important than knowing his mutations. There are many things to watch out for with CF and the doctors know what those are (certain blood work done annually, bone density, vitamin levels, liver function, diabetes etc) but by and large we treat what we get (which are for the most part are lung and digestive issues) regardless of gene mutations the treatment options are all the same.
Welcome to the site - there is a lot to learn and many wonderful people to share with here.