Fast forward 7 years and a couple of increasingly lucrative and interesting jobs...
Scala. Getting a bit bored with the Erlang ecosystem, got offered an (even more interesting and lucrative) opportunity at yet another startup, that was running on Scala/Akka/Reactive Streams. Jumped at the chance and went through what was probably the most grueling 6 months learning curve I've ever been through. Got to appreciate the benefits of a strong type system and a thoroughly modern/flexible language. Also gained a renewed appreciation for the simplicity and practicality of Erlang and it's virtual machine :)
That's where I am now. What comes next, I am not sure. Maybe Haskell or Clojure. In any case, after all this it feels like I could handle anything anyone throws at me.