I'm not on much of a 'market' and use Elixir/Phoenix for clients when I expect that either I will be primary on the codebase, or that I'll be training someone to take over.
In the latter case, I feel confident enough about Elixir that I'd train someone to use it rather than opting for a more 'mainstream' stack.
I suppose if getting new developers on-board asap is a concern, Elixir might not be the best choice. But personally if I ever were to build a product that would eventually need more programmers, I'd pick Elixir even just for the 'filter' effect. It's easy enough to pick up for a good developer, but would filter out many of the shittier devs I'd encounter if I went for PHP/Python/Ruby. and the benefits are worth it to me.
All that aside, while I am not confident that Elixir will gain much traction, I think there's a small chance LiveView and Telemetry, among other projects, might divert Elixir from the path that, say, Clojure, seems to have taken when it comes to traction.