I’ll agree somewhat, in that there will always be a market for premium properties, especially in coastal California.
Some caveats:
I think some of the less-upscale areas may take a dive (PB, OB), while the DelMar/LJ areas will do ok.
These properties are inherently at high risk, regardless of the housing market, to environmental issues. Hurricanes, tsunamis, coastal flooding, etc. It only takes one bad event to wipe out a few billion dollars of equity.