The centaur model being kind of low-poly is the main reason I don't think they planned on them ever being a race. Like not even thinking about the restrictions, but their faces are definitely lower-poly and lower quality than the Tuskarr, Dracthyr etc.
I guess they could do a Nightborne on them and spruce them up, but I doubt it. HOWEVER... if they are going hard on Nelves and Tauren living in Ohnaran together, then I can see it being a real possibility.
I think Tuskarr are currently the most likely. While it is no longer a requirement since Dracthyr, they have men and women to allow additional customization options AND they are an old fanfavorite race for EZ nostalgiabucks. And they have higher quality models (imo) than the Centaur and Drakonids.