> Home affordability is mean-reverting and the only way for it to revert is waaay higher incomes or lower home prices. I'll bet on lower home prices.
Yes and no. It is or can be mean-reverting in the short term but not in the long-term else we have a deflationary economy which would be a disaster and we'd do anything to prevent it.
> Again, just because we don't yet know the trigger which will cause this doesn't really matter.
I think you're starting from a conclusion and working your way backward. It's no different than "the market will crash again at some point we just don't know why". You need to identify the trigger and then draw the conclusion. Not the other way around.
BTW I see arguments for and against the general claim about mortgage defaults and it blowing up again.
For - housing prices are way to high, banks bought mortgage-backed securities with rates that are too low, layoffs mean defaults, etc.
Against - ongoing supply chain issues, housing supply is severely constrained everywhere in the country, low interest loans from those who keep their homes prevent them from moving, etc.
but this is all surface level. Need specifics to draw meaningful conclusions.