It'll be interesting to see if the trend towards historic preservation (maybe supplemented by the "artisanal [x]" trend) really supports these traditional skill

It'll be interesting to see if the trend towards historic preservation (maybe supplemented by the "artisanal [x]" trend) really supports these traditional skilled-construction jobs long term. A major reason people have no longer been training in areas like traditional masonry or ironwork is that the jobs weren't there. There was a huge downturn in demand due to changes in construction methods, so for a period there was a large glut of highly trained people with very little work, making it unappealing to try to break into an already overcrowded market as an apprentice. As the older generation are now mostly retiring, and there's at least a small upswing in demand due to more of a shift towards renovation (vs. the tear-down/rebuild style that characterized American redevelopment of the 1950s-80s), these trades might be worth going into again. I think there are still some pretty large question marks on the demand side, though. There will always be some demand for traditional building techniques, but how big and how steady a niche it will be requires some forecasting.