I currently see it happening with Ruby. I used it as a scripting language for DevOps tooling, CLIs, and for small web apps, but without rails.

What I see is Go pushing it out from the DevOps space and Python is more popular as a general-purpose language. Tools that were written in Ruby(eg.: Puppet) are outdated and new tools are written in Go. I still think Ruby is a superior language compared to Python, but because mathematicians used Python and the recent ML/big data hype it got more popular and got better libraries which caused an upward spiral.

While Ruby is the language I most comfortable whit and I don't see it going away in the next 10 years. I have to accept that first-party integrations will come later and later and there will be less third party libraries. That is why I'm currently learning Go and if anyone asks me what language should they learn first I point them to Python.

This is avoidable by continuing to use Ruby. Just continue to use it and contribute to the community, it's that easy. Ruby still has big businesses using it - Github, Airbnb, Shopify. There is no reason to believe it'll go the way of cold fusion. The language ecosystem is much different than 20 years ago. There are so many languages all thriving. Even Perl is relatively healthy and is a fine choice for doing many things in the software space.

I came out a little bit negative in the end, but as I said I don't think it's going away.

All these companies you listed using it with Rails and that part of the ecosystem is alive and well, but I'm not interested in it.

A few years ago Ruby ruled the DevOps/Cloud space(which I working in), a lot of tools was written in it, but with the dawn of containerization, its former glory starting to fade. Docker, k8s, or even the new GitHub CLI is written in Go. While I am happy to write Ruby code, I can't expect the same from my colleagues.

While professionally I don't think I will continue to use it much longer, I still planning to keep up with it. Before the lockdown, I started teaching Ruby at a local meetup group, and I can't wait for Ruby 3.

I dont think Ruby would ever be able to compete in that space. Even Hashicorp, the company that was born out of vagrant left Ruby and Chose Go.

I am thinking someday Crystal post 1.0 would be able to put up a fight in that space.

IMO Ruby is already being left behind. HTTP/2 is a good example. Rails doesn't support it, and I can't find anything recent saying support will be added soon. Java is notorious for slow innovation yet language level support for HTTP/2 as added years ago and enabled for basically every popular framework. Same with Python, C#, Go, JS.

HTTP/2 is essential if you want good SEO which makes Rails a non-starter for many projects already

That doesn't make sense. AFAIK with frameworks like Rails or Django you never expose their server directly to the Internet, you put a NGINX in front of it. And NGINX talks to the backend code via UNIX sockets, so support for it in NGINX is what matters.

And sooner rather than later you are going to need a load balancer anyway.

That's not really good enough, you will have http1.1 between nginx and the actual server. Many features require actual code framework level support, like server-side push, realtime streams and grpc.

Yes, but these features are not yet impacting SEO.

Do you think open source colfusion engines such as lucee[0] are worth using/learning?

  [0] https://lucee.org/

No. Avoid ColdFusion - it's a language from a bygone era when Adobe was trying to be what Microsoft is now. They failed and the ColdFusion community will die. The community, while made up of great people that I am still friends with, by and large was not interested in improving, learning new techniques, or growing beyond ColdFusion. They wanted to learn a skill and cash in on it for a long time. The language is dead and their skills are becoming useless as a result.

Maybe in 15-20 years ColdFusion will become like COBOL or ADA, where there's a bunch of code running some necessary systems and nobody knows how to maintain them. But it's a long bet for a payoff that would be much higher if you spent your time somewhere else.

If you're thinking of learning CF, only do so with the understanding that it's now a niche product mostly used in government and large companies. Learn it either as a hobby or look at the Lucee source for educational purposes. Even my last company is moving away from CF.

About Lucee ...

I actually helped the company migrate away from Adobe ColdFusion to Lucee due to a chance in Adobe's licensing. We migrated a large, 10yr old, application and all clients over to Lucee in about 1 year.

Lucee is a nice platform but I'll warn that it's not as polished as Adobe CF and there's some difference in features. You'll run into rough edges in their documentation and language implementation (especially the scripting languages). One nice thing I really enjoyed was being able to download the source and figure out how my CF code was actually being compiled into Java. It took me a few days to understand the parts I needed but I actually figured out some issues I was having. I also was able to build Lucee from source, just for learning, which was really nice.