The Marvel Cinematic Universe is pulling every superhero into battle against Thanos in "Avengers: Infinity War," and at least one of them is expected to die. There have been speculations lately as to who that might be, but franchise star Robert Downey Jr. just confirmed four characters who are going to make it to "Avengers 4."

The 52-year-old actor, who plays the role of Iron Man in the films, recently posted a set photo on Instagram, showing off his chair alongside those of returning characters Scott Lang (Paul Rudd), Natasha Romanoff (Scarlett Johansson), and Steve Rogers (Chris Evans). He captioned the photo: "New flick, new short chair. #lumbarsupport #marvel #bts." Check out the picture below:

The simple shot does not reveal any significant plot details, but it does spoil that Iron Man, Ant-Man, Black Widow, and Captain America will survive "Infinity War."

As previously reported, a casting call looking for mourners hinted a funeral scene in "Avengers 4." It did not explicitly say they will be shooting a funeral scene or whose funeral it would be. However, directors Anthony and Joseph Russo's involvement in the casting process suggests that the mourners appear in an important part of the plot.

That combined with the fact that several Marvel heavyweights are coming to the end of their respective contracts has fans speculating has many fans convinced that at least one of them will bite the dust in "Infinity War."

Then again, Cinema Blend points out that even though Downey Jr.'s social media posting confirmed their involvement in "Avengers 4," the nature of their return is still unclear. The publication notes that Tony Stark has a history of hallucinations in the previous films, so their survival in the third installment is not 100 percent guaranteed.

Unfortunately, it is still too early to predict which of the superheroes would die before the end of Phase 3. Fans will have to wait for the "Avengers: Infinity War" and "Avengers 4" to premiere on May 4, 2018, and May 3, 2019, respectively.