Having played The Elder Scrolls games from the very beginning, what I had hoped for was one huge world. One that brought all the different countries that you played in from the previous solo games together, and adding a few that were left out like the swamp world of the Lizards. Being able to travel around and pick up quests and do contracts for the Dark Brotherhood, Fighters,Mage, and Thieves Guilds in a never ending Elder Scrolls adventure.
Being a multi player environment would mean you could come across other adventurers and take on some tough spots together or get a not so dependable hireling to give you that extra boost. Or maybe be able to stealth your way into something.
Have a positive or negative reputation in the different countries and guilds that was fixable trough further actions or payoffs or whatever.
Content being added in on a regular basis, so long before you ever explored the whole world there would be new stuff brewing where you had started.
Be able to build my own little house and forge, enchanting and alchemy work areas. Have my own stable etc.
I've been able to simulate that to a small degree by using my 8 characters to craft everything. Haven't had to buy anything yet but bank and pack space and the one gold piece for the horse. It's possible to finish a lot of quests, that aren't really soloable unless you are way above the level of the quest, by waiting around until others show up.
The exception being some of the group dungeons. I hope they do some expansion of the world via sailboat or something and get away from the Craglorn thing so you can solo and group when absolutely necessary or if you just want to in the future. :-)