It's been an extremely long time since I've seen an extreme scale Kubernetes environment which didn't have some OpenStack components, and it's been a long time since I've seen an OpenStack installation which didn't include (at least one) Kubernetes cluster.
And even if this wasn't true... would it matter? We're all working towards a vision of open infrastructure, trying to serve the infrastructure needs of developers who are counting on us. Why do we have to be so tribal about it? It doesn't matter if you're using OpenStack or Kubernetes to automate your infrastructure; it matters that your infrastructure is automated and that you automated it with open source software.
In the end, it's all better when we cooperate. That's happening all over the place! Metal3.io is bringing the power of OpenStack Ironic to an API design more familiar to the CNCF/K8s community. The OpenStack Magnum community continues to make installing Kubernetes clusters on top of OpenStack easier.
Tribalism is just another form of taking your eye off the ball. Open infrastructure is winning; we can't lose focus now!
IME, openstack is being chopped up and the good parts are moving into Kubernetes. I don't think "openstack" will be a thing in the future, you'll just be using bits and pieces of it. There may come a ship of theseus moment where suddenly openstack is Kubernetes and no one notices