The forerunners created "hollow" planets to protect them from the halo array....exept they were too busy fighting the flood to get to them :/
At the end of Ghosts of Onyx a couple of spartans and Dr. Halsey are teleported to one of these worlds
and for all we know the one in the trailer may be the same one
So this is probably it because they'll probably go with the books.
Most likley yeah but we can't tell for sure