Once we have access to it, are those reflections controlled by Roughness and Metallic as in Opaque material?
Yes
Is the poping of moving objects planned to be “fixed” or is that a technical limitation which won’t be easy to change?
There are two approaches we can take - fade the reflections out when switching and then fade in again, or apply two reflections all the time. Neither of those are very appealing. But we definitely need to do something. We can also add an option to always keep using the first reflection capture cubemap assigned even after moving, under the assumption that not popping is more important than using the right cubemap. I don’t know when we’ll be able to get to this.
Are SSR planned to work with translucent materials in future?
Not at this point. SSR requires deferred shading, and translucency is incompatible with deferred shading unfortunately.