Brave New World raises a major question about the MCU: which superheroes are even left to help Sam Wilson defend Earth?

Brave New World has one post-credits scene that explains how Captain America 4 connects to future Avengers movies.

That's because Captain America: Brave New World brings adamantium into the fold. The substance shows up in the body of the Celestial that emerged from the Indian Ocean in Eternals. Now, it's the cause of international conflict, as major world powers try to control the world's only known adamantium supply.