A DICE artist currently working on Battlefield 3 has thrown together a mockup of the interior of a Halo ship using CryEngine 3.
There's a snowball's chance in hell that the Halo franchise will ever find a home on the much more powerful engine, but this mockup gives us a good idea of what it could look like. Should the next Halo game appear on the next-generation Xbox, this is probably how it'd look.
Needless to say, Halo 4 is going to be one gorgeous looking game as it is—in spite of its lack of hyperrealistic graphics. The art direction alone sells it for me, and there's no reason to think 343 Industries won't do the same with the forthcoming sequels regardless of the technological capabilities of next-gen hardware. If anything, we'll see a marriage of realistic graphics with the art direction that the Halo series has long been known for.
You can take a look at the rest of the artist's works on his portfolio page.