According to me even if satoshi is found, there won't be any impact on cryptocurrencies, crypto has went this vast. Cryptocurrencies being decentralized there's no one to control the crypto nor its creator.
Theoretically, if the real Satoshi would be back and sold all BTC he owns in a short period of time (let's say 24h), we could see a true bloodbath and incredible panic on the market. Even a short drop below $1000 would not be impossible.
Well, it would not even need to be a real Satoshi, but someone gaining control over these Bitcoins...