While it’s not nearly as robust as the Halo 3: ODST, It seems to have a lot of promissing stuff from just one small teaser

The year is 2552. Covenant forces control the city of New Mombasa. They are searching for something beneath its darkened streets. You are an Orbital Drop Shock Trooper. Your orders: Stay alive, meet up with your scattered squad, and escape the embattled city.