Put this file into ~/.bash-it/custom/

bash-it-overwrite.plugin.bash

function k8s_context_prompt {
    local kube_namespace
    kube_namespace="$(kubectl config view --minify --output 'jsonpath={..namespace}' 2>/dev/null)"
    # Set namespace to 'default' if it is not defined
    kube_namespace="${kube_namespace:-default}"
    echo -e "$(kubectl config current-context):${kube_namespace}"
}

To enable kubectl current context in your prompt add to POWERLINE_PROMPT variable value: k8s_context.