Bob, I think the word "crash" is an inappropriate one.
"Crash" implies that the whole soul collecting world will implode in the space of a day or two, like the infamous stock market crashes !
That will never happen.
Rather, the soul collecting market will just gradually fade away over an extended period of time, as our current generations move on into the next life ...
The northern soul scene - in its present form - will almost certainly disappear at some point but the genre of soul music and soul culture in all their various forms will live on forever to inspire future generations.
Truly great music like classical, blues & jazz music will always endure , and so will soul music, which is the greatest music of them all !