The actor, whose career was revitalized by launching the biggest film franchise in cinematic history, was somewhat cryptic in a discussion with Entertainment Weekly about his own future with the character he's brought to life across multiple films, but he was much more direct about "Infinity War" being a finale for some.
The Avengers face their biggest threat yet in the film with Thanos, a being more powerful and dangerous than almost any they've faced before. But world-shattering, status-quo altering hyperbole is often thrown around about tentpole projects like this, without meaning much. Fans are understandably jaded. So why should we believe it this time? Because Downey is right there with us.
"Believe me, I'm tired of every movie, you know, 'It's the end! It's Armageddon! It's the be-all, end-all forever!' And then it's... not," Downey said. "This one actually is. They're not kidding. This is a heads-will-roll scenario."
But does that mean Downey is ready to say farewell to Tony Stark and Iron Man? "I'm definitely a hang up your jersey before they boo you off the court type guy, just because I still have an appropriate fear of embarrassment," he admitted.
That led to a discussion about Tony's relationship with Pepper Potts (Gwyneth Paltrow), which has run off-and-on throughout the entire MCU. "Pepper remains the heart of the [Iron Man] story," said Downey. "I think we wanted to get back to that reality ... I always feel bad for guys who still haven't gotten their relationship together or procreated, and they're looking at the back nine... So I think there's probably some of that going on."
As he pictures a quieter life for Tony -- and we've already seen that he can pilot a suit of armor without actually being in it as he did in "Spider-Man: Homecoming" -- it's not hard to imagine an MCU without Stark, and therefore Downey, at the forefront.
"Let's compare him to me," he said of Stark. "If I was going to not be playing Tony for the next ten years, I wouldn't be doing it with no plan of what I would do instead. I don't think Tony is idle, I think he is wondering."
Adding fuel to possible speculation about Downey's exit from the franchise, he's got a pretty full slate of his own, working alongside his wife with their Team Downey production company. He's starring in the upcoming "The Voyage of Doctor Doolittle," and "then there's all this stuff down the pike. We're looking at another 'Sherlock Holmes,' we're developing 'Perry Mason' for HBO. I still want to do 'Pinocchio.'"
With the actors getting older, and more expensive to keep signing to new contracts, it only makes sense that Marvel is ready to see if a new generation of stars can hold the same power over moviegoers as Robert Downey, Jr. and the original Avengers. "The Avengers: Infinity War" might just be the opening salvo of that discovery.
Now that Downey has confirmed the "heads-will-roll scenario," it's time to start speculating on which heads he's referring to. Give us your best theories in the comment section below.