Scala is increasingly used in projects that underpin allot of todays infrastructure, for example Kafka, Spark, Akka and Finagle.
But it's not going to go mainstream because the alternatives are far more accessible.
The examples you mentioned are relative small. You know what's big? Walmart. WellsFargo. Honeywell. Novartis.
I don't think 'it will be a while' before Scala gets into those shops, I think it will be 'never' unless there is a change to how Scala is presented. As of 2016, it's still a little academic and cliquish.
Though I predict some things will change and it might gain popularity.
> The examples you mentioned are relative small. You know what's big? Walmart. WellsFargo. Honeywell. Novartis.
https://www.lightbend.com/resources/case-studies-and-stories...
https://www.lightbend.com/resources/case-studies-and-stories...
https://medium.com/@kvnwbbr/transitioning-to-scala-d1818f25b...
Which is cool, and doesn't surprise me.
But I don't see the trend lines of Scala heading in the direction they need to be in such that it becomes and incumbent language.
I don't see it as having enough disruptive power to break into the Javascript/C/C++/Java or even C# club.
My own experience is with Scala is that there is just way, way to much 'change' for some added value.
I wish they could make some tweaks to Java to incorporate some elements of Functional programming and I would be happy.
And before you blow up, it's possible to mix both styles, obviously Scala itself is an example of that.
A specific example: a lot of FP comes along with how collections, lists, maps etc. are managed and used. Lodash/underscore provides a lot of that for JS and makes a lot of JS 'functional-like'. If Java had such libraries with the mechanisms to use them (first class functions - Lambda's are not quite that) - then Java would be a lot better. Anyhow - to get the 'good things' about FP I don't think you need an entirely new linguistic paradigm.