It seems like it is coming, and the mechanics are in place, as you can have either an elemental, one of your children, or a slave in your party; however, it doesn't seem like she is planning on expanding upon it until a later date.
Unfortunately, it's the reverse.
Aside from summoned elementals, support for companions is
dropped; an expansion to the existing companion system is nigh-impossible, now or later.
Even now, you need to go into the game options and turn on a setting (which defaults to the off state) in order to enable the old behavior of having slaves/followers as companions:
Companions: Enable the ability to add slaves or friendly occupants as your companion.
Warning: This is an experimental feature, and support for companions was dropped in v.0.3.9, so there will be no special dialogue or actions involving your companions outside of Dominion.
Bringing around unique NPCs as permanent companions is not possible.
It's still on the table that unique NPCs may join you as
temporary quest/scene/area-specific companions (but you should expect heavy limitations, like Claire accompanying you during the heavily-railroaded teleport pad quest).
You can read Innoxia's explanation for this change
You must be registered to see the links
.
As an aside, elementals are no longer considered true companions either, and their implementation will be subject to another pass later on (when they get proper acquisition quests instead of spellbooks).