There have been some articles lamenting that the space isn’t available as easily anymore.

But I think it’s a combination of “toy trains” being pushed out of the “hobby” so fewer new kids are introduced to it (the Lego Train clubs get some heat and hate and generally are disregarded by the “real model trains” for example) and that the “train obsession” has other ways to discharge these days.

Many people who would have built elaborate basement models instead spend their time perfecting Factorio or Minecraft worlds (any sufficiently advanced sandbox game becomes a train simulator).

I think the period of the trains might go out of date, with a few exceptions — though it might return to fashion once it's beyond living memory.

So a collection of model steam trains might lose value, as fewer people have remember them in use, but the hobby can continue with high-speed electric trains etc.