Sad to hear but understandable that maybe the next generation is more interested in the money that land is worth now than wanting to grow plants there for the next 30 years.
Typical that the neighbors are opposed to a school opening there. Come on! Some cranky old people being mad that their day gets interrupted by cheerful screams of children playing...
Sounds like Tom and Jim are happy that some of their very old azalea and camellia will be part of a children's playground for decades.
It just goes to show that hobbyists will have to take over and propagate rare cultivars for themselves now. The mainstream big box garden centers aren't going to be doing it.
So one issue will be to save all the cultivar they developed in some garden. I know that the ASA in North East America is very keen on this.
And then from that amateurs will just have to propagate a bunch of varieties of these for whoever is interested.
In Europe, it is a big of the same with a bunch of specialty family businesses. And it could affect things like maples as well.
Only people very passionate about a specific plants can run such a business. And you can't really start one from scratch. And to be that passionate about them while your uncle or something owns a family business for them, that's kinda rare.