Agree. Bitcoin is still standing strong even after the disappearance of Satoshi. On the other hand, Larimer left Bitshares and Steemit, but these projects have been growing on their own. Which means, that Ethereum could experience the same thing right after Vitalik's death. An open source project that's decentralized, allows anyone to participate in it to improve the software for the better. That's the reason why there are many developers working on Ethereum, as well as, the community supporting it.
In the end, Ethereum could live for future generations as a cryptocurrency and smart contract platform for the masses. If Vitalik dies, then he'll be remembered as one of the pioneers of the crypto space that brought the concept of smart contracts to life. Therefore, I wouldn't worry too much about Vitalik's death (at least in the meantime). Just my thoughts