You are not forced to update (in another environment, I have customers with Rails apps in production of version 2.3, 3.0, 3.2, 4.0, 4.2) but you have the option to develop with the latest technology. In those Rails examples: I'll start new projects with Rails 4.2 and Ruby 2.2.2 and not with what I had two years ago. In the JS world, I'd start with ES6 and the latest v8, not the old one from node.