A a big non instanced world where you are completely free to do what you want, a true sandbox game where you choose to be good or evil, full loot FFA PvP without any restrictions, FPS action combat no tab targeting, jail system, dungeons, epic bosses and so on.
Make ESO a true sandbox FFA game and you will please a lot of people sick of the actual stagnation of the mmo market, expecially people who like to have fun again while playing with their friends in an online enviroment, expecially a lot of old UO players that wait for a true sandobx since trammel.
Really hope you don't simply make another WoW clone and just using the ES brand. Really hope this game will be like the ES series.