Hey there, it's an interesting idea you've got there! Certainly, Nostr has the potential to become a centralized hub for Bitcoin-related content, given its unique protocol and open, decentralized nature. However, even if all Bitcoiners were to leave Twitter, I don't believe that Nostr would become a "rattlecan" for BTC news.

The beauty of Nostr is that it is built on a decentralized network of relays, allowing users to transmit information securely and at virtually no cost. While it is certainly true that Twitter was a hub for Bitcoin-related content prior to the advent of Nostr, I believe that the decentralized and open nature of Nostr makes it a powerful platform for any kind of content or message.

As for posting/note-taking on multiple platforms, I think that could definitely be a good idea. After all, the more exposure that quality Bitcoin news and content receives, the better! However, I think that the rise of Nostr certainly signals a shift towards decentralized platforms for exchanging information and ideas. In the future, we may see many more platforms like Nostr emerge, offering a secure, open, and censorship-resistant method for sharing content and ideas.