It is doubful. Legs are completely gone when you put on the robe to avoid any clipping. And opened robes would look weird with leg animation, that's why they shortened coat for Kul Tirans heritage armor. It just looked weird below the knees with some animations because it had to be attached to leg bones.
They've been present on armors since vanilla.
This is in the game since Legion and been used for some armors. It's still painted on texture on the character's torso but the torso model changes to make armor not look like it's shrinkwrapped around the body.
Not gonna happen soon. That would require a lot of changes to how animations are done to allow for proper foot positions when wearing heels and then proper collison detection for the floors.
There's plenty of armors with 3d elements thanks to the collections system introduced in Legion.
You can't expect player armor to ever look as good as custom npc models wear or units from W3 Reforged have for one simple reason: It has to fit all races. Some compromises have to be made in order to make the system as universal as possible. With NPCs or those unites, that specific armor set has to only fit that one specific character. You can adjust everything for those specific needs.