Elm is very new in the grand scheme of things and it was considered experimental for quite a while. The recent changes show that its developers are still willing to make big changes. But I do believe it's stabilizing quickly and I wouldn't be surprised to start seeing it used a lot more, though still mostly in smaller hobbyist projects simply because even if it stabilizes it's still so new that you can't expect larger companies to risk anything on it.

Elm is a lot more experimental than Elixir, for instance. Elixir is still built on the classic Erlang BEAM virtual machine. And its syntax is fairly similar to that of Ruby, which is an immensely popular language among web developers. Elm looks like Haskell, though, which very few developers are competent with. It was originally based on FRP, which has long been considered highly speculative and theoretical. But I think by shedding FRP it's growing into a very practical language, and while it has a Haskell-lite syntax, it's considerably easier to use than Haskell.