There are already a bunch of blockchain stuff using SHA-3 apparently. If people want to drop a list of products/companies/apps that use SHA-3 (or other Keccak construction) I'd be interested!
Ethereum uses SHA-3 to begin with.
To be precise it uses variant of Keccak as NIST changed parameters of SHA-3 when they were already using it.
They started using SHA-3 before it was standardized?