Just to reply that I only briefly did Scala for less than a year, and my perspective of supply vs. demand was from attending a NYC Scala conference, maybe I was mislead to believe the supply vs. demand was this unbalanced.

As in most conferences, there are a hundred folks who say "We are hiring Scala Engineers" at every table and at the end of every talk. My employer at the time was desperately seeking Scala engineers and finding none, so they spent money to train their existing engineers.

So that's my Anecdotal evidence. I really just wanted to add that when I was young, the programming language was everything to me, it was my number one qualifier for whether I wanted to work somewhere. That is no longer true. The people I work with is now the most important thing to me.