Presumedly this is only of interest for those running Kubernetes?
So our focus is currently anyone looking to automate CI/CD on kubernetes, the cloud or any modern platform like OpenShift, Mesos or CloudFoundry which all come with kubernetes support baked in.
You can use just the CI part and do CI & releasing of non-cloud native apps if you want - we use Jenkins X to release jars, plugins & docker images using it - but doing so does miss out all the benefits of automated Continuous Delivery & GitOps promotion across environments