There will most likely be new lands to explore in DLC. Don't remember a particular spot they said this, but Todd Howard did say they want to do a lot, and fairly large DLC packs. We probably won't get to see a whole new province like Hammerfell, though.
yes Oblivion did have Shivering Isles. but if i remember correctly bloodmoon (Morrowing EP) added an area as well... if someone can remember the name of the place it would be great;ly appreciated
That was Solstheim. Morrowind also had the city of Mournhold, which, with the expansive Old Mournhold/sewers, was actually a fairly large addition as well.