Here is anecdotal evidence from my own company. As someone who is hiring developers, my belief is more and more front end development is moving to js frameworks like Angular/React/Ember and that means the backend becomes "just" an API. Rails is still a very pragmatic choice for an API, but as SOA becomes more popular, micro-services are very easily written in any language, golang, js (node), etc.

Also, as a developer you better get used to "accumulating all the knowledge and skills" but be willing to stay up to date on the trending technologies. It is the best way to stay marketable, and I think its a lot of fun too!

PM me what timezone you are in and some brief overview of your experience and contact info.