Wait, did the update finally launch for consoles????!!!!????
It didn't even "launch" for PC yet - it's still in beta test.
On point, I think that adding mounted enemies was probably too much to implement in a patch. However, I have noticed that they included mounted combat footage in the Dawnguard trailer. Most likely, that is just because the patch and the DLC are both coming out around the same time, so they are showing the feature off together. But, it strikes me that adding mounted enemies in the DLC could work since it would allow Bethesda to make more extensive changes than is possible in a patch. But that is purely speculation, so don't get hyped up.