I believe that with a high degree of probability, people will sell off their bitcoins in the event of any really strong cataclysm that threatens their life.
If it's a cataclysm where people don't have food and water - sure, they'll sell their bitcoins to buy essentials.
But if it's just a global recession - big investors like to protect their money and gold and digital gold (bitcoin) then become more attractive as they hold their value.