Keep in mind though that Skyrim got cell seperation, while Witcher 2 doesn't, and the areas that are open in Witcher 2 are huge themselves, before they are seperated into another chapter.
The reason Witcher 2 can do this is because it uses a single thread to stream background resources. Skyrim could do exactly the same.
I think Just Cause 2 also did this to make the world seamless.
In Skyrim's case, I think it has more to do with how eager Bethesda actually are to spend more money on tuning graphics. How many programmers they hire, etc. That's my personal guess.
I think the difference would be PC vs. XBOX. I don't want to talk about it until we see PC screens.
BTW,
http://brutalgamer.com/wp-content/uploads/2011/04/CompositeMountain.jpg#
I never seen better real time graphics in my life.
It's fortunate that I've seen the trailer, because if I would go by the pictures, it feels like Oblivion all over again. (Not the graphic quality. The artwork.)
I love Oblivion, but the mood of the game, I'm getting really tired of.
http://members.iinet.com.au/~amills/mmm11.jpg
http://images.wikia.com/oblivion/images/6/6a/Olfand.jpg
Legen...
http://videogametalk.com/blog/wp-content/uploads/2011/04/Skyrim-WolvesHealMace.jpg
http://www.gamer.ru/system/attached_images/images/000/321/363/original/4.jpg
wait for it
http://3.bp.blogspot.com/-jCsuz8hIZaw/Taw8_KgG_uI/AAAAAAAAATQ/h2157kOMiMY/s1600/es-1.jpg
(And one more time.)
http://brutalgamer.com/wp-content/uploads/2011/04/CompositeMountain.jpg#
...dary.
The change is actually quite dizzying.