A lot of people have been saying it since Oblivion's launch, so hopefully it is being addressed already, but level scaling is something I would really not like to see in the game. The reasons have been stated before well enough that I won't rewrite it, but I think the game would turn out more satisfying without it.
A bit more diversity in what a player can do would be a welcome change. Now, though it's kind of an anathema to say so, but I'm generally happy with some of the streamlining that seems to be the trend for some of the newer titles. Mass Effect 2's system worked wonderfully for what the game was trying to accomplish, D&D 4.0 cut out a lot of largely unnecessary things while preserving the essence of them. I didn't like the direction Oblivion took with it, however. It seemed too rushed, and produced unnecessary skills while reducing others to trivialities, and cutting out some that were deemed unnecessary. Considering TES's past marketing as a world where the player is the centrepiece of a setting with minimal boundaries, those little things that the player has the liberty to do -- enchant their own gear, become more of a skilled alchemist, devote specialization or lack thereof for visibly different play styles -- really make the difference.
As a more aesthetic aspect, I really, truly hope the models and animation changes improve things. Those soulless faces are what keep me from buying Fallout: Vegas. I don't think it's absolutely necessary to try to meet the standards of some of the more high-end graphic RPGs out there, but even something slightly different from the present would be a fantastic.
The last major concern I can think of right now is the reliance on voice acting. Again, for games like Mass Effect, Fable, etc, full voice acting works very well with the setting and the atmosphere those games are good at creating. But in the case of TES, I can honestly say that I would much, much rather read through large amounts of text rather than hear a few sound bites from the NPCs, which inevitably results in a far more shallow pool of dialogue, given the kind of money voice acting demands.