Full warning: We're talking Marvel's Eternals spoilers below! As with any new movie in the Marvel Cinematic Universe, Eternals has its fair share of set-up for what will come next. The film not only introduces a fresh group of heroes that will no doubt appear in other Marvel projects, despite not really interacting with other Marvel characters in the pages of their comics, but also brings in other heroes that aren't Eternals, teases even more that aren't seen, and adds a huge wrinkle to the cosmic side of the MCU. We'll break it all down below.
First let's address the Eternals themselves, by the end of the film the team is divided. Having stopped The Emergence from taking place on Earth and preventing the birth of the celestial Tiamut, Sersi, Phastos, Kingo, and Sprite appear to be ready to live on Earth as they did for many years (Sprite now turned fully human and no longer an Eternal) while Thena, Druig, and Makkari fly off into the cosmos on their ship The Domo to find other Eternals. Their Earth-bound Eternals dreams are immediately dashed though as their defacto boss, the celestial Arishem plucks them from the planet and takes them with him, displeased by what they've done. The trio flying off into space however find themselves with company as Starfox (aka Eros, brother of Thanos) and his associate Pip the Troll offer them a hand on their journey.
All of this considered it seems like Marvel is gearing this up for an Eternals sequel down the line, considering none of these characters are really associated with the already established major players on Earth that remain. That said, Marvel hasn't outright committed to a straight Eternals sequel just yet, though the film's final title card after the credits roll does note the "Eternals will return."
Perhaps Marvel is putting all these pieces on the board in the far reaches of space for something that will perhaps be further teased in Guardians of the Galaxy Vol. 3. Filmmaker James Gunn has made it clear that this is his last chapter with that team but once he departs the galaxy exploring parts of the MCU are the wild west, with a lot of potential players and stops along the way.
This isn't the only thing that the movie does to set up a sequel and other spinoffs though as the final post-credit scene features Kit Harington as Dane Whitman considering picking up his family heirloom, the ebony blade. Comic readers will know that Whitman and this sword will go on to become the Black Knight, a character that has been an Avenger and a Hero for Hire in the pages of the comics. The most surprising thing about this scene though, besides Whitman not actually appearing in full Black Knight gear, is that a voice from off camera asks him if he's sure that he's ready for that before he can pick up the blade.
What was unclear at the time and wasn't made official until the film was released was that this voice belonged to none other than Academy Award winner Mahershela Ali, previously announced to be playing the part of Blade in the Marvel Cinematic Universe. The film does not make it clear that this was Blade however, so finding out that it's him makes it an even bigger surprise than the fact that it's not even addressed.
It may seem surprising that Blade of all people would be speaking to Whitman as he prepares to take up the mantle, but the pair have a history in the pages of Marvel Comics. Both Blade and Black Knight were members of MI13, aka Military Intelligence, Section 13, an official UK agency that handled paranormal entities and goings on in Marvel comics. Perhaps what Marvel is teasing here is that Blade is gathering some of the more paranormal-leaning characters in the MCU for his own team, perhaps MI13 (the scene takes place in the UK after all) or maybe even the Midnight Sons.
As with the post-credit scene an set-up in Shang-Chi and the Legend of the Ten Rings it's unclear when we'll actually see any of this teasing and set-up play out on the big screen or on Disney+. So far Marvel's announced slate of content stretches into 2023 with no official dates for Blade, Eternals 2, or anything else that seems relevant.