Yes, but that’s not how it currently works, so that’s the part that needs work. How are you going to do this from within the Discourse admin interface. How are you doing to scale down the blue container while spinning up the green container (systems don’t have infinite resources, so before starting up blue you want to reduce unicorn workers in green.) Or you can just go for green is down, and now blue goes up.
There are a lot of things which need to be figured out and worked out. Both from a technical perspective as an administrator perspective. The single click upgrade from within the admin interface is a valuable feature.