If the fun and pleasure in this Hobby is not shared far and wide, it will die. The TCA absolutely needs to HELP drum up customers/Hobbyist!
As someone who has been in the hobby since about 1969, I feel confident saying that no, train collecting and operating will not die as a hobby. There were some fairly lean years in 1969 and the early 1970's.
There will always be a group of people who are interested. The number of manufacturers may shrink significantly, but there is plenty of merchandise already out there. There may be a return to small "basement companies" making the stuff we need to keep our trains going.
The TCA never was, and never should be a manufacturer's support organization. It's the manufacturers who should be supporting the TCA, not the other way around.