WARNING: The following contains spoilers for Black Widow, now playing in theaters and available for streaming on Disney+ Premiere Access.
Natasha Romanov has been one of the major mainstays since Phase One of the Marvel Cinematic Universe, with the hero getting one last spotlight in Black Widow -- alongside her "family" of former Russian spies, including Yelena, Alexei and Melina. While Natasha's story concluded in Black Widow, the post-credits teaser of Black Widow sets up a future role for her sister in the MCU, and it's with a team that's been teased beforehand.
Black Widow largely focuses on Natasha, the heroic Avenger and the most prominent Black Widow. However, there have been plenty of other Black Widows over the years -- including Natasha's one-time undercover "sister" Yelena Belova. Thanks to Yelena, Natasha gets the chance to reaffirm their bond as well as work to free the mind-controlled other Black Widows from their conditioning. She's even able to help successfully liberate them, allowing Yelena -- as well as their "parents" Alexei and Melina -- to take them all to freedom.
The post-credits sequence for Black Widow teases the future of the spies, or at least one specific one. Taking place after the events of Avengers: Endgame, Yelena visits a makeshift grave for the woman she considered her sister. Allowing herself to die to earn the Avengers the Soul Stone, Natasha was one of the only people not able to be resurrected by the heroes when Hulk snapped. A grief-stricken Yelena has a moment of silence and is promptly joined by Valentina Allegra de la Fontaine, who appeared in The Falcon & The Winter Soldier. She effectively pitches Yelena on working with her -- hinting at her growing plans for the MCU.
In her last appearance in The Falcon and the Winter Soldier, she recruited John Walker -- aka US Agent -- to her employ, giving her a Captain America-esque figure. Now, with Yelena seemingly being courted for a position, Contessa has gained her Black Widow stand-in. It looks increasingly like Val is replicating the actions taken by Nick Fury in the early days of the MCU and is recruiting her own team of super-powered individuals who can help her protect the world the way she wants to. This adds more fuel to the speculation that Val will be responsible for the MCU's incarnation of the Dark Avengers.
This confirmation also positions Yelena firmly at the center of whatever changes are coming to the MCU. She'll likely be a useful asset in whatever plans are going into motion from Val, especially considering her contacts with the rest of the Black Widows who exist out there, as well Alexei and Melina. It seems increasingly like a dark variant of the Avengers are being built while a future generation of heroes also takes the spotlight, setting up a potential conflict over who truly protects the future of the MCU, with the new Black Widow right at the heart of any potential conflict.
Directed by Cate Shortland, Black Widow stars Scarlett Johansson as Natasha Romanoff/Black Widow, Florence Pugh as Yelena Belova, David Harbour as Alexei Shostakov/Red Guardian, O-T Fagbenle as Mason and Rachel Weisz as Melina Vostokoff. The film is now in theaters and available on Disney+ Premier Access.