Wanna bet and check back in 5 years?

I love Ruby but I'd still cautiously take that bet. At the same time, I don't think it's easy to come up with terms for a fair judgment of who wins. What does Crystal being the future of Ruby mean? To me, I think in the specific cases where people who like Ruby want Ruby - mostly webapps with great dev ergonomics and productivity - Crystal will definitely start to gain ground, because both Amber and Lucky are lovely frameworks with a lot of excitement behind them. But will it take over Ruby? Probably not.

Adding to d3nj4l's answer, that Ruby also has a great community of active and passionate (yes, in the proper sense passionate of the programming language) developers.

I think Elixir has better chances of taking over some of the Ruby pie from this perspective as the Elixir community is a lovely and helpful as the Ruby one.

Without such community it is very hard to build momentum and most programming languages remains great options but limited to a small number of projects.

I like Crystal and played with it a little bit. I tried to use it in production for a small project where I offloaded some tasks from Rails into Crystal small programs.

I'm game

OK, let's get it on.

I'm bookmarking this. God willing, we can check back in 5 years.

Would job postings and TIOBE be enough?

Possibly. I mean, would maintaining legacy applications count towards growth?

This was honestly what crossed my mind as I read that article as well. They're basically asking for Crystal and it's already done. Static type checks, performance, fibers and channels. As a bonus things like compile time null checks.

While they're looking for some features from Crystal, the point of adding some of this stuff is to have it without the expensive port to another language or platform. Crystal lacks metaprogramming, which would be hugely disruptive for many applications, and every application dependency would need to find a Crystal replacement.

I think what's being played out is the maturation of a platform. Ruby and Rails have been around for a while now and there are many large Ruby codebases out there. The Ruby standard library is fairly comprehensive. The dependency management debate has largely been settled. So, a focus on performance and taking advantage of multi-core systems is a natural area to shift focus to. Adding a progressive, opt-in, type system can help navigate large applications.

At the end of the day, all of this new stuff can be ignored if you want. Ruby will still be Ruby. But, if you do want to use one of these new features, you won't have to go through the time-suck of porting to a different language.