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.
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.