Will Robert Downey Jr Be the Secret Weapon in Avengers: Secret Wars? Everything We Know So Far

Marvel is playing the long game with the Multiverse stuff, and all signs point to the big swing happening in Avengers: Secret Wars. The wild part? The chatter around Robert Downey Jr. coming back to the MCU, not as Tony Stark, but as Doctor Doom. Yes, really. There was even a photo circulating on X on Nov 22 claiming RDJ in Doom mode tied to Avengers: Doomsday. Marvel, of course, is saying nothing.

What is actually official right now

Marvel has only confirmed the title and the release date. Everything else is coming through trades, agency slips, and the occasional social media 'oops we posted that'. So treat the rest as developing, even if some of it looks locked in.

Release date and when cameras roll

Secret Wars is dated for December 17, 2027, and it is positioned as the finale of Phase Six, basically closing out the Multiverse Saga. Production has not started. The plan floating around is to start shooting in mid-2026, after Marvel gets Avengers: Doomsday out the door in late 2026. London is where the next Avengers shoot is expected to happen in that window.

So, who is in this thing?

The cast is shaping up like a greatest-hits pull from across timelines and franchises. The Fantastic Four are up front, and the RDJ-as-Doom chatter is the flashy headline for a reason. Here is how the lineup looks based on reports and the handful of teases we have gotten so far:

• Robert Downey Jr. as Doctor Doom (reported; a social media post on Nov 22 showed a new Doom look tied to Avengers: Doomsday)
• The Fantastic Four cast Marvel has already been parading around: Pedro Pascal, Vanessa Kirby, Joseph Quinn, and Ebon Moss-Bachrach
• Benedict Cumberbatch back as Doctor Strange
• Sebastian Stan as the Winter Soldier
• Wyatt Russell as U.S. Agent
• Lewis Pullman as The Sentry
• Sadie Sink, quietly outed by a Deadline piece about her 2026 West End debut, which noted she would 'join the cast of the next Avengers picture that shoots here in London later in 2026' — and the Avengers movie filming then is Secret Wars. She is also set to show up first in Spider-Man: Brand New Day, with her character still under wraps. The way this is framed, Marvel clearly sees her as a key part of their X-Men build-out.

Worth noting: despite the endless speculation cycle, there is no official word that the Russo brothers are steering this. Marvel seems laser-focused on Doomsday first, then Secret Wars.

What the story sounds like

The current chatter lines up with a Battleworld riff — think a patchwork reality formed from smashed universes — with Doctor Doom on the throne after he takes Kang off the board. That setup opens the door to memory-wiped heroes, familiar faces working under Doom, and a lot of 'wait, that is an alternate you' confrontations. It also tees up the X-Men as the next phase of the MCU, with Doctor Strange back in the mix (his exact role is still being figured out).

Marvel boss Kevin Feige basically laid out the mission statement over the summer. In his words:

"Not just to round out the stories we have been telling post-Endgame, just as importantly, and you can look at the Secret Wars comics for where that takes you, it very, very much sets us up for the future. Endgame, literally, was about endings. Secret Wars is about beginnings."

If they stick that landing, Secret Wars is not just an ending — it is the MCU pressing the reset-and-go-bigger button.

The bottom line

Avengers: Secret Wars hits theaters December 17, 2027. Casting beyond the Fantastic Four and the usual MCU anchors is still being kept in the shadows, but the RDJ-as-Doom drumbeat is getting louder, the Sadie Sink slip almost certainly ties her to the Avengers shoot in London next year, and the story framework points squarely at Battleworld chaos. All of which sounds like Marvel finally cashing in on the Multiverse hype — for real this time.