New content will be added through Anthem's live service updates. The first "act" of post-launch content, called "Echoes of Reality," will launch in March, a few weeks after the game does. The roadmap calendar so far only shows three acts, with the latter two yet to be revealed.
Echoes of Reality will feature three updates—"Evolving World," "Stronger Together," and "The Cataclysm"—that will add new events, rewards, strongholds, story missions, and the ability to form guilds, as well as a major Cataclysm for players to contend with. BioWare hasn't stated how long this first act will last or when the second act launches, but it's clear that the developer plans on continuously adding new content for players to explore.