Check out the image below to see confirmation that the first "event" will be called Echoes of Reality, and will be available in March!
Anthem is a new shared-world action-RPG from EA's BioWare studio where players can team up with friends as Freelancers - the bold few with the courage to leave civilization behind and explore a landscape of primeval beauty, confront the dangers you find and grow in power with every step. The second update, Stronger Together, will presumably focus on new co-op and social features - likely the guilds and leaderboards listed in the roadmap. They are seasonal activities, not one-shot endgame missions.
For more on Anthem, be sure to check out a breakdown of what Anthem's Endgame content will look like from a gameplay perspective, as well as 10 minutes of a Legendary Contract on Anthem's challenging Grandmaster I difficulty. He described them as "content that you engage with for weeks", which would come out less frequently than new challenges, events, and strongholds. At this point, players will be able to take part in daily, weekly, and monthly challenges, and unlock "Anthem's" Grand master, Grand Master 2, and Grand Master 3 difficulty tiers.
Endgame features will be available once the player reaches level 30, the maximum level in the game. Crafting blueprints will also enable you to obtain other gear and personalisation items, with said blueprints, crafting materials and coin earned for completing endgame objectives. Legendary Contracts will also be made available for players hungry for more hard, multi-part adventures. Finally, the third update will introduce Anthem's first Cataclysm, a type of time-limited world event said to be partly inspired by Fortnite's long-game seasonal narratives. Contracts will allow players to increase their reputation with different factions, granting them access to crafting blueprints.