Does Docker's expansion into orchestration and clustering endanger CoreOS and maybe other players? Certainly. Is it the same approach? Definitely not. The CoreOS approach to containerization using Docker, and now Rocket, is novel. I haven't considered it for any of the architectures I'm presently building for companies - I prefer to let the operating system do what it does best, and build my services on top using containerization.
I was worried about what Docker's plans for clustering entailed leading up to today. I have been using Mesos for the better part of a year, and see it answering many problems that reach beyond the container model. I think people should do as you suggest, and re-evaluate this on two fronts: 1) Swarm is separate from Docker, so we can continue to deploy Docker through Mesosphere Marathon onto Mesos as we've been doing. 2) Because scheduling is pluggable - as the source code validates for us - we can work in Mesos as we see fit.
As for the proposal, I vote to keep Compose (and the fig codebase ;) ) separate. It will be much easier to add the hooks necessary to do cluster management between Compose and Swarm without risking regressions to Docker.
Also - what has become of the Docker Governance Advisory Board? I think the ratification of a standard / specification would go a long way to solidify trust in the industry (much like CoreOS is trying to do with their App Container proposal).
- Paul