I do have some concerns about Docker Inc. and Mirantis (which now owns Docker Swarm I believe), yeah. Swarm is pretty mature though, and while I don't think it's going anywhere soon, I don't think we'll get any more core features anytime soon.
For Lunni, my plan is to add support for another orchestrator while keeping the developer experience of just working with docker-compose.yml. I really didn't want to do K8s, but given it's essentially an open standard now, it should be a safer bet than Nomad. I guess we'll see when I can get to it!
My gripe with nomad was that it didn't have init containers. You were basically forced to either have an endlessly growing job specification file or put consul-template in every single container image.
My concern around Swarm is around the Docker corporation, which appears to be struggling.
As a competitor, we have Nomad, but with the recent IBM acquisition, I'm concerned about Nomad's future.