It needs a lot of work but it won't happen, the mounted combat we have now is a big concession.
I like being able to hold a strike and charge at the target then release as I pass.
But my ideal situation there would be to say, continue moving while swapping melee for bow, twisting around and loosing an arrow to finish.
On paper the mounted combat we have now seems to let you do that, but in practice it's awkward and clumsy.
But where does the list of needed features end?
Mounted combat is a Pandora's box.
Bethesda are skittish about the horses for a good reason, they could easily add storage/saddlebags for example but they have stated that making the horses too important would amplify their flaws and create an unending cycle of players calling for this or that to be added/fixed, tweaking and patches until the horses become this monster feature overshadowing everything else... or words to that effect.
As it stands players don't care too much about horses in Skyrim, they're just a peripheral feature.
Mounted combat has made players care a bit more about horses and start looking at horses more closely, so seeing their flaws more readily... and caring more about those flaws... and consequently start asking for those flaws to be addressed in preference to features that Bethesda considers a higher priority than horses.
The reason being that the potential list of features they could add to horses is never ending... so better not to start.
I'm not sure I agree with your anolysis. The reason horses were relegated to a peripheral feature isn't because people didn't care. Horses were heavily scrutinized and picked apart almost as soon as the game was released. They were found to have a number of issues including, among others, difficult controls, forced third person and the total inability to do anything on horseback. They were relegated to a peripheral feature not because people didn't care, but because people found them to be poorly implemented and more of a hassle than running.
Mounted combat makes them less of a hassle and that's a big part of why people wanted it. Unfortunately, yeah, people have issues with mounted combat now that it's out. Why? Part of it is that many of the original issues of the horse are still present and make it more difficult to use. The other part is that it feels incomplete or missing aspects one might expect to find in mounted combat.