I am not worried. I think if there is a market for tinplate trains, someone will always fill the need.
For example, Pat's Trains has recently offered for sale on this forum several new SG trains based on MTH 400E locomotives pulling 4 passenger cars. Among those offered are an Army set and a Navy set, which I have on order.
And lets not forget the truly custom Standard Gauge locomotives and passenger cars being built by Jim Waterman. I have placed an order with Jim for a set of 1952 Olympian Hiawatha passenger cars, which I will be pulling with my MTH Milwaukee Road Super 381E.
So let's not worry, there still are craftsmen like Jim and dealers/companies like Pat's Trains/MTH ready and eager to fill the need for tinplate trains. We just need to keep them in business by placing orders with them for new tinplate trains!