Where does the Dawnguard dlc take place? In Skyrim or outside of it or both?

I believe it's still in Skyrim.

Part of it will take place within the Soul Cairn.

I saw some crazy new castles lol

i have not heard of it, what is this soul cairn you speak of?

Soul Cairn is a realm of Oblivion unaffiliated with a specific Daedric Prince, a realm of tombs and undead which is supposedly ruled by a race known as the Ideal Masters.

hhmm i hope i get to fight them in large numbers

I thought Oblivion was sealed off from Nirn for good after the events of TES IV?

Each daedric prince has their own realm of Oblivion each individual. In TES IV you shut close the oblivion realm of Mehrunes Dagon (the prince of destruction). This means other realms of oblivion will still open up such as Sheogorath's oblivion realm in the shivering isles expansion in TES IV and possibly the Soul Cairn in the dawnguard expansion in TES V.

Apparently Whiterun is destined to have a huge Red Vortex form above Dragonsreach... Near the end of the Trailer.... Now I do enjoy wreaking havoc in Whiterun but I would thoroughly enjoy ruining everyones life at once....

Sounds good

this may sound crazy but i think it takes place in skyrim.. yep. i don't know why i think it does, just feels like it does (no sarcasm)

There are clear signs that it takes place in skyrim with the natural look of ice and forest much like those in the rift. But there is a small scene where a portal/staircase to another realm is opening up which symbolizes them stepping into this oblivion realm Soul Cairn. So it might be 50/50 a bit of new realm a bit of some skyrim looking scenery maybe island off the coast of skyrim or something it is not known yet have to wait for e3 i geuss.

I think you`re right.I found this link which may prove you to be correct http://theparanoidgamer.com/new-skyrim-dawnguard-information looks like an excellant DLC

Actually, all the player succeeded in doing in Oblivion was forbidding the Daedra from entering Nirn on their own accord. Not just Mehrunes Dagon's world was affected -- no Daedra can willingly enter Nirn (only Daedric Princes are an exception). Daedra themselves can still be summoned.