For the last 5 or so years I have been on teams that heavily used Ruby. Ive been noticing (and this is all just personal observation) that there is a definite trend away from Ruby to things like node, clojure, scala, elixir. Is it dying, i dont, think so, is it going away, i dont think so. In 2 years will other developers look at ruby, like an overwhelming number of ruby devs i know look at php, probably, im already seeing this happen.
Ruby made heaps of developers lives better, I know it made my life better, but I feel the world has moved on and its getting farther and farther behind.
And the argument about jruby being fast and having concurrency i feel is moot, its like saying erlang can be written as a lisp because of LFE, sure it can, and its well done, by people much smarter than myself, but nobody i have ever heard say “jruby has concurrency” as far as I know has actually used it in production. The attitude is always “when we need concurrency we will switch to it then” but by the time they need concurrency they have a monolithic rails app, with heaps of mutable state/shared resources, an underlying architecture that isnt thread safe, and way to many gems that dont have up to date jvm based counterparts, if they have counterparts at all.
There is quite a bit of talk here (in melbourne australia) these days about elixir and phoenix, many of the bigger local ruby names are looking more and more into it. But that will be interesting too, I can see many of them getting into it, being all "this is so close to ruby and rails, its like im productive right out the door, and then I think they will run into the concept of an erlang supervisor and back the NOPE away.
TL:DR - ruby isnt dead, its gonna be around for a long time, people will just look at it with the contempt that many ruby devs look at php these days.