I would really like new skills lines and new skills added to current skill lines. I feel this would add more excitement to the current classes and playstyles that have largely remained the same for years. It's a bit odd to have a new class like a Necromancer come out, and then in order to play him correctly, fill his skill bars with bow/staff abilities from practically every build prior; playstyles and builds feel like they are stagnating and all too similar with each other. And why blame the players, to not take a bow on a stamina dps build in pve is a silly thing to do as you'll be losing a crazy amount of damage from not choosing the tired poison injection/hail of arrows--even though it's very odd to have a Necromancer *require* a bow thematically.
New dungeons and zones seem nice, but I'd like new, varied ways to interact with those dungeons.
(Also, please add a permanent pet to Necromancer, Zenimax. I'd give up the ability to throw floating skulls at enemies for an axe-wielding skeleton that cleaves enemies any day)