Gary,
I am sorry to hear about your dad. It is nice he is able to keep some of them though.
Personally, I think we who appreciate the true Cornish should be working toward spreading the word on these beautiful birds. If you have the room, keep them going, your dad has obviously put a lot of work into his birds and it is producing some excellent results. It seems a waste to just drop the whole thing with such an investment in them.
Even if this breed does seem to be a niche, there are a growing number of people who DON'T want the freakish CRX. That is what interested me in the breed to begin with. They are THE original meat bird, and they need to be preserved.
So, add that to the fact that your dad has worked them into a very nice BLR variety and they are a hot commodity the last couple of years with the Wyandottes, so why not jump on that wagon and get this variety on it and moving them into more popularity.
If you need a place for them, I can make room
My 3 little ones from your dad's flock need some buddies. You know, birds of a feather and all.