Depends on what you're doing, really.

Rust is lovely for security-sensitive code - I'm writing a customer identity management system with Rust+Postgres+Redis.

Go is... acceptable... for "glue" code where PHP would've been used a decade ago and Perl before that - all the successes of it I've seen fall into that sort of pattern.

Elixir is great when you need to think about networked, stateful systems on the scale of a rack of machines - it provides many of the components to help you design systems at that scale.

So... as ever, they all do quite seriously different things. I don't think many people need to build the sorts of systems Elixir is good for - it'll always have its niche in large-scale communications systems, though. A good many webapps fall into the patterns that Go is good for - take user input, munge it, send it to some backend system. A fair bit of code that drives the foundations of what those webapps are built on will eventually be written in Rust.

I understand where they are supposed to fit, but the problem is there are so many existing tools to fill the same needs already.

As an example Erlang and Elixir both fit essentially the same bill so it seems to me what was already a small niche is just getting fractured.

Elixir is just alternative (Ruby-ish) syntax for Erlang, as much as people have hyped it up - Erlang code can call Elixir code and vice versa with essentially no abstraction cost. In fact, the most popular web framework for Elixir is heavily built on Erlang code.

That was my point exactly. Before if you really needed the benefits of running on BEAM then you would have chosen Erlang. Now that subsection will fragment between Erlang and Elixir. Today Elixir developers still will lean heavily on the interaction of Erlang libraries until someone in Elixir-land needs something that isn't supported so then they will re-invent that particular wheel in Erlang and thus the cycle continues ever on.

Then as you stated yourself Go is being used in areas where PHP & Perl were used before (as were also Ruby, Python, and Lua). So now there is just one more fracture there. Of course this is especially interesting since Go was supposed to be a better C or C++ then that should have placed it pretty squarely in systems programming land, yet is has managed to gain more traction as a glue and web services languages, ergo it ends up competing in this space when it probably should have competed more with C/C++/Rust.

Rust; as a systems programming language still has to compete with C/C++/ObjC in this space and considering that "all the systems" already run on these languages that is one huge challenge to change the guard there. I'm not saying that Rust is bad, rather just that I think it's long term outlook may actually be rather bleaker than other languages due to these challenges. Quite frankly D had some great concepts and improvements as a systems language over C++, but it is still barely a blip on anyone's radar.

If an individual is just trying to learn and expand their horizons then any of these languages are great to pick up. If, on the other hand, they are banking their future career on one then none is a sure fire bet right now. One would honestly still have more luck with a tried and true like Java.

Personally I enjoy picking up new languages just to see things from a different perspective and continue learning. Heck I spend much of my free time coding in Crystal which hasn't even hit a 1.0 launch so that adds pretty much zero improvement to my career prospects. :)

I wouldn't bank a career on a language anyway, so.

However, as Elixir is just another skin for Erlang, switching from Elixir to Erlang or LFE or whatever the next language for that runtime is will be simple - the issue is really BEAM and OTP, as few of the skills learned around them are cleanly transferrable to other runtimes and frameworks.

I suspect that Go will be around for a while by sheer force of inertia at this point - we're 5 years since 1.0 now and it still seems like there's new major projects being started in it every day.

Rust is... interesting, but I think it'll always have its niche. As much as people like to riff on the RIIR crowd, there's actually a somewhat decent ecosystem of reimplemented libraries and systems in Rust already, and now that Rust code is part of Firefox it seems unlikely that Mozilla will stop supporting it for a long time to come. It also seems to not be a zero-sum game - rather than stealing devs from C++, it's brought a lot of developers from "non-systems" languages into the "systems" space.

Exactly. If Elixir didn't have to compete with Clojure, Rust, Go, Node, Scala and Kotlin it might have had a chance to become mainstream. Beyond the hype job stats are the ultimate indicator.