Skyrim on multiple disks wouldn't work very well. There's too much re-use of assets, meaning they'd have to be included on each disk. Not to mention where would you divide it up? Exterior world and interiors? Every time you walk in or out of a city you have to switch disks? No, multiple disks wouldn't be practical for Skyrim.
Lol, the games saved to a storage device would mean no need to swap discs. The games install on 360 is less than 4gb. Its clear your perception is still stuck thinking that we have to play off the disc at all times. We can easily install games to HDD's or memory sticks. I have other games on 360 with bigger installs, and double discs. Hell Forza 3 is two discs and tells you to install disc 1 & 2 when to fire it up the first time.