The fact that Ruby is the language chosen to implement these tools is the proof it's not just for Rails. Also, Docker may become more popular but I doubt it is

The fact that Ruby is the language chosen to implement these tools is the proof it's not just for Rails. Also, Docker may become more popular but I doubt it is going to replace Vagrant. There are just too many times where you need a full VM instead of a container process. Not every problem can be solved with containers.