How will new versions of Apps deploy?


 Reading a few articles about Applications and one thing that caught my eye was applications updates. 

If a host has an update for their hApp will it/can the new update be deployed only among designated hosts or would an update be default updated across all hosts?

If a Dev wanted to use Canary deployment and choose certain users for it can they switch hosts to match traffic for said deployments or would Holo hosting just soak up the resources needed regardless?

Would you say Holo is a mutable or immutable server, or does it have the characteristics of both?