Satoshi Nakamoto never revealed himself to the public, so his absence didn't have a negative effect over BTC's price. With Ethereum, it's different. So many people have associated ETH with Vitalik Buterin these days. If he's dead, you can bet market prices will dump real hard due to panic selling. I know the project has other people behind it, but things won't be the same as they were with Vitalik on-board.
I don't think we must to bet anything because Ethereum suffered fud in the past about Vitalik's death.
Vitalik had to make a self-fie to prove that he was not dead.
Vitalik really want you to know "He isn't dead".