Personally, I love the Elder Scrolls games and think they are among the best RPGs ever made. There is, however, one exception that I'd love to see improved on in the next game.
Morrowwind, Oblivion, Skyrim, etc. have a plethora of NPCs in the game, and it is very nice to be able to interact with pretty much all of them, which Bethesda does a good job with. But you can't develop any relationships, aside from with the Jarls in Skyrim. Marriage is cold and quick, and then interactions with your spouse are stiff and limited after the ceremony.
How nice would it be to develop friendships and romantic relationships in the game, if you wanted to? I am not suggesting TES games should become like the Sims. Nor am I suggesting we should force players to have emo gush fests with NPCs. What I am saying is that it would be nice if the game felt less lonely, companions were more conversational and deep, and romances were a lot more deep and fleshed out. The Dragon Age games do a pretty decent job with this, even though they are a little gift-centric.
Then, there could also be more personal interactions with those NPCs. Perhaps your dead horse is at your front door one morning as a message from someone who hates you. Maybe you receive a message in the mail from an anonymous admirer. Perhaps someone you saved earlier in the game shows up at your house and offers to watch your children while you're away. Perhaps a shop keeper in the town you live in mentions that your wife was by earlier and seemed in good spirits today. Little things to make it seem like the game is wrapped around the player character, and to bring out the relationships in subtle ways.
This is just another element I feel would round out TES games a lot. Roaming around in the world alone, with a companion who doesn't really interact with me, and with no one at my house(s) to interact with much either, makes the game a lonely place and so I wanted to suggest this for future games. I look forward to the next TES title (assuming it isnt an MMORPG again), and thank you for reading.