We're talking about the law, not some guy's blog. If you believe that bank accounts and Bitcoin are securities under the law, then you are incorrect. It doesn't matter whether some guy calls bank accounts securities on his blog. That doesn't change the law.
Saying the law could change is literally always true, it means nothing. Will it change? You could make an argument for Ethereum, and I tend to agree that the community is overconfident about the regulations around Ethereum and other coins. However for Bitcoin specifically the SEC has been very clear and consistent in stating that it is not and has never been a security. Their justifications are sound. So no, it almost certainly won't change for Bitcoin.
Copyright covers the specific number in addition to the general intellectual content of the number. You could say it covers a family of related numbers. That's stronger than just covering a single number.