I don't think Levitation will or should return, it feels weird to say that because I loved it so much in Morrowind. However, levitation being in the game limits dungeon design too much, its not just about open towns or anything like that, think about the caves, forts, and especially the elven ruins in Oblivion that had open rooms with multiple levels where getting up a level required going through a trap or puzzle. So many gates and bridges would have been useless if levitation was in the game, any player could just float up to where they need to go and ignore parts of the dungeon.
That entirely depends on how the levitation is implemented. The spell could be high-level and there are multiple ways to design a dungeon part to be one-way only. E.g. have a clutter trap or cave-in that could only be removed/cleared from one side.
I think you're thinking too much inside the box of Oblivion. If Skyrim dungeons were like Oblivion, then levitation would be bad. But have in mind that levitation didn't ruin the dungeon design in Morrowind or Daggerfall - in fact, you actually acquired some new factors with regards to how you'd design an imaginative dungeon. Not to mention the potential existence of Anti-magic fields, zones in dungeons that can literally cause all magical effects to be dispelled and silenced. You'd fall down to your death if you levitated into such fields.
I, for one, do hope that levitation is in. Besides, what about other things in Oblivion that you could use as substitutes? Getting to places meant to be "inaccessible" because you had 100 Acrobatics or stop using manual lockpicking because you got the Skeleton Key. If Alteration and Restoration was of equal level, e.g. 100 each, Feather was more or less useless because you could just take Fortify Strength instead for additional benefits.