The Eternals trailer hinted at Captain America’s death and it should put an end to the rumors that he’s returning to the Marvel Cinematic Universe in the future. Steve Rogers’ story came to a close in Avengers: Endgame, with Cap returning to the past to live out his days with Peggy Carter following the Avengers’ defeat of Thanos. However, a report surfaced earlier this year suggesting that Chris Evans would reprise his role as Cap in other MCU films despite having fulfilled his contract with the release of Endgame. Eternals seems to shut those rumors down rather permanently.
In The Falcon and the Winter Soldier, Sam Wilson mentioned that Captain America was gone (and he was, but not dead). The rest of the world, however, believed the First Avenger was living on the moon. Both of these scenarios hint at the possibility of Cap’s return. After all, he’s living in the past and not dead like Iron Man, so it’s not like he can’t time travel back to the present day if absolutely necessary. The conclusion to Steve’s storyline in Avengers: Endgame seemed permanent, but the MCU (and the superhero genre at large) could always find a way to bring him back since being “gone” is still rather vague.
On the other hand, the Eternals discussing Cap being gone had a more conclusive ring to it and they, more than anyone, would know the truth for sure. The cosmic alien beings have been around for a long time. Considering they have been overseeing and guiding humanity for centuries now means they are well aware of what happened with Captain America. They wouldn’t bring up him being gone and joke about Ikaris becoming leader of the Avengers in his and Iron Man’s place if Cap’s absence was only going to be a temporary one.
The Eternals also have no personal stakes in Steve’s fate and their discussion about the future of the Avengers without him seems rather final since they are more privy to the bigger picture. They’re probably laughing at the conspiracy theories about Steve being on the moon as well. The Eternals’ mention of Captain America is a relief after rumors suggested he might return. Avengers: Endgame wrapped up his story and gave him a happy ending. His return to the MCU would not have gone over very well. His reappearance would also undermine Sam’s journey towards becoming Captain America.
Kevin Feige shut down rumors of Evans' return and Eternals is going one step further to reiterate that Cap is well and truly gone. With the Eternals, the MCU is moving forward with a new kind of team instead of picking back up with old ones. Instead of looking to the past, the immortal group represents the future and what’s to come with Phase Four beyond the original Avengers. Knowing the Eternals’ wealth of knowledge and information about the timeline of events, their mention of Captain America offers the finality that is very much needed following his departure, hopefully putting the speculation surrounding his return to rest for good.