We've got to define "unlivable". What if statistically, everyone's house will be destroyed by flooding, forest fires, etc.. let's say, twice in their lifetime. How can the math possibly add up if a house's price requires a 50 years mortgage? At some point, something's gotta give and that kind of odds will happen in a timescale shorter than many living people care about.
Also, wasn't there something about, you know, caring for the generations to come? Maybe I misremember...
with the current TFR rapidly approaching 1.5 children per woman virtually everywhere in the northern hemisphere, even if it remains stable (it will not, it will continue to decline), its population will shrink to 1/10th of what it is today in less than 250 years.
there will be plenty of empty houses for the generations to come.
Also, wasn't there something about, you know, caring for the generations to come? Maybe I misremember...