Why would you need to wait a generation? More like a couple of months. People who are moving to luxury housing live somewhere now, which is less new. When they move out of there, someone else can move in, etc. and on down the line freeing up multiple housing units one by one at ultimately different prices. It adds to the total housing stock in the city immediately.

And no, “all” the luxury housing is not being bought by investors. Even in places where this is a problem it is nowhere near “all”. Investors can also just buy existing housing. Once again, what you anti-housing folks are claiming as a problem of building new housing, is a problem that is going to happen anyway and will be even worse if we don’t build new housing.