First I'd like to add a better screenshot (slightly corrected dynamics):
But now to the main part: I highly doubt that it's the ship.
I guess/hope it is a temple like structure.
I think they are gonna resurrect the silo/pyramid idea from the early ALIEN scripts.
I'll try to explain;
This was an early concept of the top-entry of the pyramid:
This was Giger's take on this:
And these are from Giger's work for Dune shortly done before Alien:
To me those Giger designs are related to another. He even put that spiky trench on the pyramid so that the astronauts could climb to the top opening.
Now look at this:
And now this:
To me this looks almost like the Dune thingy and the astronauts enter at the face.
We all know that there will be a giant face inside some temple in Prometheus.
There is even talk of new Giger murals, like in the original Alien concepts.
Prometheus originally took off as an Alien remake and it still seems to incorporate some elements from early versions of Alien.
To me the structure in the trailer looks a bit like a combination of the first Dune image and the structure from the ridleygrams, just with some wall around it.