we're finding federation is great fun, fwiw. Our groups have lots of regulars we'd never have met otherwise.
The other fun thing about federation is that when you ban an idiot coming in from another server, you never have to see them again and they can post their last word out there in the ghost version of the thread that you never have to think about.
Federation is definitely here to stay. Its a good idea.
Implementation details do matter however. I could see something like Kbin.social winning out as PHP-developers could be more popular / available than Rust developers, for example.
Hard for me to look into the future. Weird decisions ripple out over time. People are definitely "onto something here". So I'm trying to keep an open mind to the different possibilities.