I would hope that since this is the companies second foray into an xbox 360 title with the availability of xbox live's pay for service that 2 to 4 player co-op is even attempted. Rummaging through dungeons and all around exploring the world or cyrodil in Elder Scrolls: Oblivion would have been amazing but it was a little bit ahead of it's time then to EXPECT it to be integrated into the game. Skyrm is looking to be a graphical powerhouse and I honestly don't know what to expect.
One thing I do know is that every game that has fully integrated co-op in their game has had to make sacrifices from somewhere. I will give two examples I can think of off the top of my head. Borderlands off host on xbox 360 the graphics takes a hit and halo 3 the graphics take a hit all around. So in theory skyrm in co-op only would have to take a slight hit from somewhere and when it comes to voting it should be something to consider.
But if it did have fully integrated co-op it could possibly be one of the best games ever made.
Please keep in mind that I am talking about fully integrated co-op and not multiplayer.
Fully integrated co-op is simple it's like super mario bros with a second or up to four players, it's inexpensive.
Multiplayer is like WoW which has adversarial plus raid instinces etc etc (too much work).
Co-op is just allowing for a second player to tag along......not all the other things that come with a multiplayer game when skyrm is a year away, that is asking too much.