WandaVision's seemingly offhand reference to Carol Danvers (a.k.a. Captain Marvel) was actually set-up for Monica Rambeau's role in the upcoming Captain Marvel 2. The MCU's inaugural Disney+ series premiered its first two episodes in January and is nearing the end of its nine-episode run, with the finale set to release on March 5th. Captain Marvel 2 is currently scheduled to release in November 2022, with Nia DaCosta attached to direct.
Since WandaVision revealed Westview resident Geraldine was actually Monica Rambeau, S.W.O.R.D. Captain and daughter of its founder Maria Rambeau, fans have kept a close eye on her development throughout the series. The character made her first appearance in the Marvel Cinematic Universe as a child in the '90s-set Captain Marvel, where she was portrayed by Akira Akbar, and Mad Men actress Teyonah Parris took over the role as an adult for this series. Rambeau has had multiple superhero aliases in the comics, including taking over for Danvers as Captain Marvel, so audiences have been eager to see what direction Feige and Co. choose to take her in. Traveling through the Hex in the latest episode seems to have triggered something in her, but the exact nature of her new powers remains unknown.
Marvel has already announced Parris will reprise her role in Captain Marvel 2, and a brief moment in WandaVision episode 5 suggests a serious strain in her relationship with Brie Larson's Danvers. When Agent Woo and Darcy mention Captain Marvel, Rambeau pauses, grimaces, and changes the subject, and Parris suggests in an exclusive interview that this was some intentionally vague foreshadowing:
There was a reaction when Carol's name was brought up. Everybody has their own take on what that might be. I do know that I was announced to be joining Captain Marvel 2, so Monica Rambeau will be there with Iman and Brie, Captain Marvel and Ms. Marvel. I hope that we will have the chance and the space to further explore that relationship that was set up in the first Captain Marvel and that we're kind of teasing at here. There is space for that to grow.
Little is known about the plot of Captain Marvel 2, partially because the film is confirmed to include both Rambeau and Iman Vellani's Kamala Khan, the star of the Disney+ series Ms. Marvel that is nebulously set to debut in late 2021. With Rambeau's WandaVision arc still ongoing and Khan's character yet to be introduced, as well as plenty of other MCU content that could have multiverse-altering consequences ahead of it on the release schedule, it's hard to know what things will look like by then. But it certainly seems like something happened to sour things between Rambeau and Danvers since the '90s, when the two were quite affectionate.
While there haven't been any direct hints about what could have driven a wedge between them, it's reasonable to speculate it has something to do with Monica's mother. Maria Rambeau was Danvers' best friend before she became superpowered, and a WandaVision episode revealed that Maria died of cancer after the events of Avengers: Infinity War, while her daughter was lost to Thanos' snap. Monica regenerated in the hospital to learn her mother had been dead for years, and with how long Captain Marvel had spent away from Earth, there might be some lingering resentment there. Fans will have a while to wait before they find out for sure, but it's gratifying to know that time spent reading into every second of WandaVision will eventually pay off.