There have been plenty of hints provided through external material and interviews that point to Wanda and Pietro Maximoff being mutants in the MCU, at least after The Walt Disney Company acquired 21st Century Fox in March of 2019. Marvel Studios Visual Dictionary began this long-overdue retcon by describing the origin of Wanda's powers as potentially having been “unlocked” within her:
“Whether it altered her or merely unlocked something latent inside Wanda, the Infinity Stone on Loki's scepter bestowed incredible powers of the mind.”
In The Wakanda Files, an in-universe journal written by Shuri, it's noted that HYDRA chose Sokovia citizens with specific “genetic anomalies,” as they made the best candidates for their experiments with the Mind Stone. It is incredibly likely that these “genetic anomalies” could be a dormant mutant gene that the Mind Stone could trigger if the subjects survived.
Most prominently, Marvel Studios President Kevin Feige said that three questions would be answered in WandaVision concerning Wanda's powers:
“Who else is aware of that power? Where did it come from? Did the Mind Stone unlock it?”
Again, using the same word as the visual dictionary, the Mind Stone may have unlocked Wanda's powerful abilities instead of giving them to her. Many fans have now found that the latest trailer for WandaVision seems to show the exact moment that Wanda's amazing abilities were unlocked.
In the latest trailer for WandaVision, there is a moment in which Wanda can be seen looking at something brilliantly yellow off camera. Her hair is an unkempt brown, she wears raggedy gray clothes, and her eyes seem to be red from crying or exhaustion.
Soon after this shot, the yellow object explodes in front of her, where it can be seen that Wanda is in an enclosed space. We see more of her distinct clothing, showing how baggy it is and how the sleeves reach to her hands.
Fans had compared this to the Captain America: The Winter Soldier post-credit scene, which showed the aftermath of the twins, Wanda and Pietro, having been given powers by HYDRA through the use of Loki's scepter and the Mind Stone.
What stands out almost immediately is that Wanda's clothes from this post-credit scene match the clothes she's wearing in the WandaVision trailer, specifically the color, bagginess, length of the sleeves, and in addition to her eyes and hair. It would also make sense if she had been exposed to the Mind Stone in this same room or at least one similar to it at this HYDRA facility.
WHAT THIS MEANS
At this point, it seems almost inevitable that WandaVision will reveal that her powers were not given to her by the Mind Stone, but rather that they were unlocked by the Infinity Stone.
It is unknown whether WandVision will actually use the term "mutants." Still, it is undeniable that the source of her powers will indeed be explored in the show, especially since what she's displaying is a far cry from simple telekinesis or telepathy.
Elizabeth Olsen even teased that Wanda's Eastern European origins would be explored, which seems to include HYDRA's experiments on herself and her twin brother going by the latest trailer. Could fans perhaps see her family history explored in the show, too, including her own? Wanda and Pietro only spoke of their parents regarding their deaths at the hands of one of Tony Stark's black market weapons.
Who knows, maybe the Maximoff twins might have some iron in their blood.