If insurability becomes a crisis, I'd expect it to reduce housing availability and raise prices for competing (insurable) properties.

Of course it wouldn't happen in isolation, so there are other massive forces to consider.

Maybe wide swathes of formerly-occupied (but now uninsurable) land would sell cheaply enough that middle-income people could build inexpensive semi-disposable vacation cottages, like the old days.

GP's assertion of population collapse in five years is a bit extreme for me!

I'd expect to see a surge in self insurance. These areas are so valuable already in a lot of cases where rich people are content to pay six figure property tax bills. Especially with cost of construction being a fraction of that property's value.