I think both standard gauge and tinplate are relatively small niches in a small hobby. There has been a lot of production in the last 30 years of tinplate O and standard gauge, by both MTH and Lionel and various joint efforts over that time.
As an example, rather later in life, I bought my first new tinplate O from Lionel's current production about 11-12 or so years ago (the freight and passenger sets), and just bought my first ever standard gauge train and track (Lionel Classic 381 and State cars from 1989 or so) recently. As I've been in the model train hobby for about 40 years, I'm an example of the possibility that some of us develop an interest in standard gauge and tinplate rather late in our time in the hobby.
A hiatus in production and withering of existing inventory might increase demand for new production in a few years time as availability diminishes. However, I would guess these products will remain a small niche within the overall toy train/three rail hobby, with modest demand.