I addressed that point in the post. Unless you replace all the implementations of SHA-2, the deed is done. People will choose SHA-256 and SHA-512 because that's what they've always known.
> without requiring the adoption of new hashing code
I should have made myself clearer: I recommend SHA-3 for new projects. I wouldn't recommend people to switch to SHA-3 if they are already using SHA-2.
I really don't agree. Rijndael and DES are different algorithm. SHA-512/256 is a made-up algorithm that you need to be aware of. Again I'm talking about "misuse" here. SHA-2 is vulnerable to misuse even if SHA-512/256 is not.
I might be a bit. Although, I don't feel like it's too far from the kind of misuse we've pointed out with nonce re-use in AES-GCM or nonce re-use in DSA/ECDSA.
Anyway that was my point! Just wanted to write it up :)
> without requiring the adoption of new hashing code
I should have made myself clearer: I recommend SHA-3 for new projects. I wouldn't recommend people to switch to SHA-3 if they are already using SHA-2.