For some reason this just makes me really hope dwarves can ride mabari.
That amuses me so I will give you a "like."
Actually wouldn't dwarves be more likely to ride those bronto things? They were canonly used as dwarven mounts. I kind of hope they are added.
But yes, if you look closely at the concept art with the mountain and the Inquisitor riding on something, you'll see that the "something" has a short tail and pronged horns/antlers. If it's not a halla, it's something similar. But, it may be like the raven/crow in that other concept art, and we'll discover that we only get horses after all. they may not have time to implement anything else. After all, a horse and a deer move quite differently, so it wouldn't just be modeling and texturing work, but also animation work.