The environments in the screenshots aren't made up entirely of lumpy carpet-like heightmaps, so they're definitely a major improvement over Oblivion. And no, it's not Gamebryo. That's been confirmed for so long, so many times and by so many different sources that I'm amazed you'd claim otherwise.
EDIT: And if we're going to be talking semantics, I might as well go ahead and point out that Gamebryo isn't the main reason why Oblivion's environments looked the way they did.
Call me stubborn, but I'm still not totally convinced that this is not a Gamebryo based engine. Look at Todd Howard's comments about their new engine being Gamebryo 2.0, along with the statement he made a few months back:
"Speaking with EuroGamer, Todd Howard, fresh from his role as Executive Producer of Fallout 3, made it clear that although the studio would be using the engine that they have built three of their four previous games upon, they’ve been working on squeezing every last drop of performance out of it. “It started with Morrowind, we went to Oblivion, we did a lot between Oblivion and Fallout 3 because now we had final hardware,” he explains, “with Oblivion, we had six months on final hardware, so Fallout 3 technically does a lot more than Oblivion. The new stuff is an even bigger jump from that.”
Why exactly would he lie about using a heavily modified version of Gamebryo, unless he was afraid of the backlash of the community who was sick of it. Combine that with the fact that the enemies in the screens (especially the were-yeti looking thing), bear an uncanny resemblance to those in Oblivion. Also, when you look at the details and the textures in the outdoor scenes (the snow ones in particular), the textures and details look very Gamebryo like. In my opinion, they have tweaked and modified and re-written the engine so much that they are calling it a new engine. That would explain why they were torn between calling it Gamebryo 2.0 and "a new, internally developed" engine.
Anyway, I don't want to sound like I am complaining, because I think the game looks amazing. They obviously addressed the character models, and that was my main gripe with Oblivion and FO3. As long as the animations and LOD scaling are a huge improvement, which I believe they will be, then I will be completely happy.