Marvel Studios head Kevin Feige recently teased a meeting between the Avengers, X-Men, and Fantastic Four at the Baxter Building in Avengers: Doomsday. Following the release of The Fantastic Four: First Steps,

While the hood of his forest-green cloak obscures his face, the stranger holds in his hands the familiar mask of Doctor Doom. Yup, this scene sets up exactly what you think it does: It tees up Robert Downey Jr. as Doctor Doom.

The "Doomsday" plot leak also seems to confirm the big fight at the X-Men mansion in the universe where Monica Rambeau ended up at the end of "The Marvels." That universe's anchor being is a Professor X (Patrick Stewart) variant that Doom wants to kill. Interestingly, Earth-616 and Earth-10005 -- where Monica is -- are on a collision course.