The appearance of the mutant would serve to introduce the X-Men to Phase 4 of the UCM.
With Phase 4 on the way. Captain Marvel 2 is part of the next stage of the Marvel Cinematic Universe. The film starring Brie Larson is one of the most anticipated by Avengers fans.
Although details of the plot are not known, as read in various Marvel forums, the villain of the sequel would be the mutant Rogue.
MCU fans think it’s not crazy, since in the comics, Rogue was raised by Mystique; who introduced her to the world of crime. It is at this moment that she confronts Captain Marvel, who absorbs her powers and memories.
It is known that Captain Marvel is the most powerful character in the MCU and taking away some of her powers would balance the Avengers.
In addition, Rogue would serve as a link to introduce the X-Men in the next film phases. Something that Kevin Feige confirmed at ComiCon 2019.
Rogue
Anna Marie D’Ancanto alias Rogue, is a fictional superheroine who appears in comics published by Marvel Comics. She is a mutant commonly associated with the X-Men. However, before belonging to that group she was a villain in the service of Mystique.
https://twitter.com/liliths_cradle/status/1101186276013805570?s=21
i think rogue debuting in captain marvel only would work out well if they make her the main antagonist and give her a big role and not just some cameo. but you never know with marvel studios 😐
— caro (@616ROGUE) April 9, 2020
Introducing Rogue as an antagonist in a Captain Marvel sequel would actually be a great way to set her up for a future X-Men movie. Have her permanently absorb some of Carol's powers – it would actually give Carol some genuine flaws and conflicts to overcome.
— Michael O'Connor (@NoWordCount) November 26, 2019
Btw Rogue has to start out as a misunderstood antagonist being manipulated by adults. That's what she was when she was introduced, that character development is vital. If not Mystique, Destiny could be her adopted mother and introduce them both as antagonists in Captain Marvel 2
— #Funisinfinite ✊🏿✊🏾✊🏽🖤 (@SpideParker) January 31, 2019