Are NixOS and GuixSD the incoming Linux distros of DevOps?
Some articles, including this one give some arguments why docker is popular:


  In a nutshell, here's what Docker can do for you: It can get more
  applications running on the same hardware than other technologies; it
  makes it easy for developers to quickly create ready-to-run
  containered applications; and it makes managing and deploying
  applications much easier. Put it all together and I can see why Docker
  is riding the hype cycle as fast as I can recall ever seeing an
  enterprise technology go.
  
  Moreover, for once the reality is living up to the hype. Frankly, I
  can't think of a single company of any size that's not at least
  looking into moving their server applications to containers in general
  and Docker in specific.


My personal view is that a tool could be successful if it will solve a (major) problem. For example, a half year ago I gave a presentation of docker in the company, the developers had some doubts until they experienced a issue that it was not possible to run all microservices on their local machine.

The same is applicable to the question: 


  Are NixOS and GuixSD the incoming Linux distros of DevOps?


It depends whether these distributions will solve a (huge) problem.