The Marvel Cinematic Universe is about to head into Phase 4 once Black Widow finally lands in theaters this November. Most of the plot lines to come in this next slew of movies and Disney Plus series are relatively unknown, which has led to a plethora of theories. After Black Widow's release, WandaVision will be the next project fans can see, hitting the small screen in December. What's to come for Wanda Maximoff and Vision is unknown, but some are speculating their show will introduce one of the biggest villains in Marvel Comics.
Screen Rant has proposed a new theory suggesting the series will bring Magneto into the MCU. Now that Marvel Studios officially owns the X-Men franchise, characters from the stories are speculated to start entering the universe sporadically. Most comic book fans know Magneto is the father of Wanda and Pietro Maximoff, so his entry into the MCU could be done through a connection to Scarlet Witch.
In Avengers: Age of Ultron, moviegoers were introduced to the powerful twins, and their parents were alluded to as citizens of Sokovia. It was revealed their mother and father were dead after being killed by a mortar shell that hit their apartment building. Screen Rant believes it is possible these aren't Wanda and Pietro's birth parents, but perhaps ones that adopted them.
WandaVision is rumored to be dealing with alternate realities, which is always an easy way around plot holes. In a different reality, Wanda could have her comic book mom and dad or a different family situation altogether. Some think there's a way to bring in Evan Peters' Quicksilver from the Fox X-Men films though a different timeline. With Pietro dying at the end of Age of Ultron, it would be a tricky workaround to try and bring in a completely different sibling, especially by a different actor.
Although only briefly alluded to in X-Men: Days of Future Past and more so later in Apocolypse, Michael Fassbender's Magneto is the father of Quicksilver. Either one of the important men in Wanda's life could link to the other, and it's likely that fans will see at least one of the characters appear in WandaVision.
If Magneto does not show up in the Disney Plus series, it is possible he can come into the MCU through Doctor Strange in the Multiverse of Madness, which Scarlet Witch is also confirmed to be in. The movie is set to delve into the multiverse, which is full of alternate universes and timelines, another perfect way for the villain to enter Phase 4 and beyond.