Speculation has been rampant that a major star from the Marvel Cinematic Universe will appear in the final episode, following comments made by the Vision actor earlier this year.
He told Esquire that the mystery figure is someone he has "longed to work with" for his entire life, prompting guesses ranging from Benedict Cumberbatch's Doctor Strange to Chiwetel Ejiofor's Karl Mordo.
However, following the reveal of a new White Vision in this week's episode, fans are now wondering if Bettany was referring to none other than himself.
At the end of WandaVision's penultimate chapter, acting SWORD director Tyler Hayward (Josh Stamberg) reveals the rebooted android - lacking his usual colour scheme - and prepares to send him into Wanda's surreal sitcom world.
That means it's quite likely that the "real" Vision will come face-to-face with his mysterious successor in the series finale, resulting in Bettany sharing a scene with himself for the first time.
The actor continued: "Of all of the characters that we were trying to keep secret, a lot of them got out through leaks, there is one character that has not been revealed.
"We have some amazing scenes together and the chemistry between us is, I think, extraordinary. It’s just fireworks on set. So, I’m really excited for people to see that stuff."
It's understandable why these comments stoked such anticipation for a jaw-dropping cameo, but since the introduction of White Vision (which had not been leaked beforehand), they can now be interpreted in an entirely different way.
We're not entirely ruling out a guest appearance from the likes of Doctor Strange, Mordo or Captain Marvel, but this latest development has certainly cast doubt on what had once seemed like a rock solid theory.
WandaVision concludes this Friday (5th March), as Elizabeth Olsen's Scarlet Witch faces off against Kathryn Hahn's powerful sorcerer, Agatha Harkness.