Rod,
I'm a railfan and I'm not happy with the way CHS forced the GLRR out, but I think you are way over estimating the economic impact of the change. Far from an average stay of 1.5 days, I would guess that the average tourist spends a couple of hours riding the loop, then another hour buying a few post cards, a sweat shirt or hat and possibly lunch, then hitting the interstate to continue on the way.
The average tourist isn't going to care whether there is a steam engine on the train, a US built diesel or a German, or Chinese diesel for that matter. They will enjoy the ride, enjoy the view, tour the mine and have a great time. I expect that fewer than 5% will be bothered enough by a lack of steam to stay away.
So, if the CHS is planning on maintaining the same capacity as this year, expect to see diesels or at best, a diesel pushing C&S number Nine at the head of a bunch of ex C&TS box car coaches or covered flat cars!
It sucks, but life ain't always fair!