[pjungwir]

In my opinion Rails is the fastest way to build web applications, and the best framework for iterating as you react to new business knowledge. I don't see that changing soon.

Investing in a JS framework seems like a natural complement to your existing skills. Angular & Ember are great fits with Rails. I also like Knockout, which has an easier learning curve.

Another great fit would be Chef, which would leverage your Ruby skills and let you improve how you're deploying the Rails apps you're building.

If you don't have a lot of experience in low-level languages, I'd explore those for the learning. C is a lot of fun and very different than Ruby. iOS would be a practical choice, and apps make very rewarding side projects, although it might be a big change of focus for you. If you want to stay on the server side, I'd find something you can optimize with C or Rust: some critical code, or maybe a Postgres stored procedure.

[markuz]

This is a great advice if you want to be a generalist. I'm a specialist.

Take a look in this article, it illustrates pretty well the differences. http://www.nczonline.net/blog/2014/07/15/generalists-and-spe...