I wanna say a few things I wanna see with the Horns of the Reach update. Feel free to say what you wanna see as well!

PvE-wise:
-Khajiit passive to also include spell critical. Give us more diversity with magicka races than the awful Altmer and Dunmer. Their lore just makes them overall jerks.
-The new sets from the dungeons to actually be good.
-Buffing the other magicka classes to be more on par with sorcerer.
-Buff stamina builds majorly.
-Allow for more tank diversity than Dragonknights.
-Ease the gap between normal and veteran content. Normal is painfully easy compared to vet.

PvP-wise:
-Viper, Selene's, and Velidreth proc sets need nerfing. They can stack and one-shot people in non-CP campaigns and Battlegrounds with the lack of CP reducing damage taken.
-Add a CP-version of Battlegrounds.
-Make the Warden ability Cliffracer dodgeable. If people can dodge force pulse, they should dodge that.
-Add another CP campaign to ease the amount of people being in Vivec. People are in that campaign the most mainly because it's a fairer fight and procs sets can't simply melt people.