Yeah, that kind of surprised me too. I would have expected a move to Node, or some other javascript framework.
I did think the quotes from Zed Shaw and Paul Watson were good. Zed's point, that Rails and Django are server-rendered frameworks written before the client-side, front end era, does sum up why I think interest in Rails is declining.
And Paul Watson's comment explains why, in spite of this, I'd still be inclined (for now) to use Rails for a lot of projects. If you're mainly dealing with web forms, in a light to medium traffic app, you don't necessarily get much from the front-end heavy frameworks. They add complexity, and can slow (bog) you down.