What happens when theymos is gone (for any reason), that is a goo question.
I hope he already prepared some plan to make sure forum survives.
The closest thing I saw to a decentralized forum that worked was Steem(it). It ran quite well (it still
exists) and had good SEO for some time. The crucial part making that possible was obviously that there was a web front-end run by the founders, but the content was stored in a decentralized manner. So there were a couple of alternative web front-ends.
Main problem with Steem was tokens they used to reward members for writing posts and comments, and I think this project later forked into separate project with different token.
Only way for forum to work in decentralized way long term is if there are no tokens involved, and you should not have to pay to make posts.
I think also Nostr has a lot of potential. It solves the "server-dependency" problem of earlier decentralized social networks and could be combined with a blockchain approach in theory.
I agree with this.
It's possible, and I could even imagine clients or bitcoin wallets that have something like integrated chats or forum extensions, maybe as sidechain or second layer.