This thread 
I’m so excited about the prospect of some of you becoming published authors!! 
I can definitely vouch for those mentioned above too, Margaret 
@ohm ran one of the first Rails forums and when I found that I was too busy with the Elixir Forum, he kindly took over the running of the Ruby forum I was running at the time. He’s been a Ruby dev for quite a while so will have seen a lot of what’s been and gone, and what’s coming up - that angle will be quite beneficial for a Ruby 3 book imo.
Although I haven’t known @CinderellaMan anywhere nearly as long I’ve known Ohm, Kamil is a well-liked member of the Elixir community and you can see how popular his video series was here. There’s also quite a bit of interest in Cryptocurrencies right now (and I would definitely include a chapter or two explaining exactly what they are and all of the in/outs etc).
I wouldn’t bet against Ruby 
Ruby is one of those languages that I think will be around for a very long time, and as we’ve seen with Ruby 3, it is getting better and better all the time. The Ruby community is also one of the most passionate I have ever known, and I am sure they will continue to refine and push Ruby over the years, even in the face of languages being created or backed by huge tech giants.
Have you thought about reading @chrispine’s book Margaret? I highly recommend it! I think after reading it, you may well become hooked! 