I've made a load of 3D models of 1/300 and 1/600 WW2 costal forces craft which I was putting up for free on some of the Facebook naval groups. I've stoped doing that now as one of my friends said things like that were likely to put him out of business.

Model railways I think are a bit harder to manage in 3D modelling, at least as far as locomotives are concerned. But I have seen some lovely 3D printed carriage, wagon and loco bodies so I agree it is a matter of time.