During the QuakeCon at Home opening event, Bethesda and id Software announced the first campaign expansion coming to Doom Eternal. Check out the teaser trailer for The Ancient Gods: Part One above, which gives a small glimpse at some of the new environments and fights the Doom Slayer will be facing.
The Ancient Gods storyline will take place after the events of Doom Eternal, where hell and heaven have been thrown into chaos thanks to the Doom Slayer ripping and tearing through both of them. Here's how the new campaign is described by id:
Your victory over Hell’s armies pulled humanity back from the edge of extinction, but it came at a cost. An imbalance of power in the heavens requires the true ruler of this universe to rise and set things right. Wage war across never-before-seen realms of the DOOM Universe and fight against new demons in your never-ending battle against the forces of evil.
The Year One season pass of Doom Eternal mentions it provides access to the first couple of expansions, meaning even more adventures of the Doom Slayer might get explored following The Ancient Gods: Part Two.
A full reveal of the expansion's first part, plus hopefully a release date, is slated to happen during the Geoff Keighley-hosted gamescom: Opening Night Live digital event on August 27. It was also confirmed recently that Doom Eternal would be getting Xbox Series X and PlayStation 5 releases, with current-gen owners receiving free upgrades.