that is a black swan. And we all know that ethereum's genius is vitalik, and when he dies a lot of people will lose their faith on ethereum. Because vitalik buterin is the brain behind the ethereum so it will really affect the price.
Vitalik may be the brain behind the Ethereum project, but there are other talented developers which are currently working to make Ethereum better than ever as a cryptocurrency for the masses. If Vitalik dies, then the project would go on as intended, due to the full support from its community. Of course, people who don't understand how cryptocurrencies work, will quickly associate the founder's death with the death of the Ethereum project itself. However, we all know that's not the case, since Ethereum was designed as a decentralized cryptocurrency.
This means that Ethereum will evolve for many years to come. Vitalik is only there as an advisor, but it could easily be replaced by another person. What really matters is the longevity of the project as a decentralized blockchain system that could execute smart contracts without middleman. If Ethereum remains as is, then it'll be successful in the future.
Nonetheless, Vitalik's death may cause the price per ETH to decline for a while, until everything settles. By then, people will actively demand the "Ether" cryptocurrency to interact with other ERC-20/ERC-721 tokens or dApps. Which means that Ethereum will become a widely usable cryptocurrency in the long term. Just my thoughts