Warning! This article may contain spoilers for Black Widow. Read at your own risk!
Yelena Belova makes her debut in Black Widow and as much as everyone has their eyes set on Natasha Romanoff, the scene-stealer is definitely her sister as she marvelously gave justice to her character considering that she is not even the titular character. The film ultimately sets up her future in the MCU and here is how that was made possible.
To start, with Natasha Romanoff’s death, there would definitely be a space for Yelena to be the new Black Widow of the MCU as there would be no other candidate closer to her to don the title despite there being a lot of widows in existence. As the Red Guardian tells her, she is the greatest child assassin that there ever was as she is ruthless and efficient.
Her skills could easily match that of Natasha’s and while she could definitely use some tactics from her, she has got her own set as well. What Natasha’s only edge from her could be the experience of Natasha with the Avengers and her amazing split-second decisions that would almost always be precise and well-calculated.
Yelena definitely has a bright future in the MCU with her skills and abilities. If she were to follow the footsteps of her sister, probably sans the hero poses Natasha makes as Yelena utterly despises such, she could easily be the new Black Widow.
However, things change up with the appearance of Contessa Valentina Allegra de Fontaine because from the looks of it, they already did some missions together basing on their conversation during the post-credits scene. While there are a lot of hints that point to Val establishing the Dark Avengers as she also recruited John Walker as the US Agent, having Yelena with her is definitely a plus on her team,
The short scene by the end of the credits rolls also establishes the arrival of Yelena in the upcoming series of Hawkeye where Clint Barton will be passing the baton of being Hawkeye to Kate Bishop. It is also possible that with Yelena being recognized for her skills and abilities, the Young Avengers could also be formed especially with Billy and Tommy, Cassie Lang, and Kid Loki already introduced in the MCU, and Miss America confirmed to be appearing on Doctor Strange in the Multiverse of Madness.