Alliance Raids, I can see that happening. Normal Raids from Coils and Alexander, yes as well... though possibly less urgently. Trials and later normal raids? Well, that's where it gets complicated with some of them having significant shifts in the background; there's also less to see in general, so I can see this being last for priority.

In any case, it will likely be a progressive implementation to include all the dungeons and some of the more "notable" instances (mostly Alliance Raids because they're essentially really big dungeons).
It's probably in the works, but something we'll have to wait patiently for them to implement retroactively into older content.