I'd be surprised if the Bo'ness and Kinneil doesn't survive. Apart from the rides, there are Thomas and Santa events, railtours via mainline connection, income from films and Network Rail training, and the Scottish Railway Museum. No real like competition in the area, which is right in the middle of the central belt - half of Scotland's population within 30 minute drive (I've just made that up, but suspect it's not too far off). It's a pity that Birkhill mine closed, but visiting that was a bit of a niche market anyway, with a lot of climbing (on steps) involved. I don't know if they do market it this way, but linking with the Wheel and Kelpies more or less on the doorstep would make a varied trio.