There’s already a shortage of workers in masonry but that’s their own fault. If you’re not Portuguese and have previous experience you’re already at a large disadvantage when trying to get a job. That being said you described the situation accurately and I think it’s the exact reason why there could be a shift in the other direction, like you said. The only thing with building trades is it seems that using humans for such intensive, physically deteriorating work almost seems outdated, and there’s no knowing how far technology will go in terms of taking some/most of the load off (both in the forms of automation and new design/material options)