Guesting on the Happy Sad Confused podcast, the Russos -- who are directing both pictures -- were asked about the reports that the title of the fourth Avengers movie was actually a spoiler pertaining to the future direction of the Marvel Cinematic Universe itself, thus necessitating that it remain a secret for now. Joe Russo more or less acknowledged that was the case:
"It is certainly part of the concept of the title is that it’s advancing the narrative. So we’re gonna sit on that until we feel the time is right and when people have absorbed the first movie enough."
That sounds like we won't know what the title is until at least some time after Infinity War is out in May, once the bulk of the fan base has had a chance to see it. Originally called Avengers: Infinity War II, the fourth film will end Phase 3 of the MCU, and will usher in a new era in which Marvel Studios head Kevin Feige has acknowledged that the universe will look a lot different.
The Russos also confirmed in the podcast that Steve Rogers/Captain America will be deconstructed in Infinity War and embrace "the spirit of Nomad," his mid-1970s identity, with Joe adding that he's "a character without a country." But the brothers were less forthcoming about whether they are working with Brie Larson as Captain Marvel in either Avengers movie, simply saying, "There will certainly be some curveballs thrown at the audience." (Don't worry, guys, Feige already confirmed Larson's participation for us).
As for what lies beyond Avengers 4, the Russos were thrilled to hear the news that Marvel is finally developing a standalone Black Widow movie, with Joe saying:
“Yeah, we’re very happy for that. I mean, it’s such a rich and interesting character. There’s so much to explore with a character whose history was as a villain, and you know, Scarlett does such a great job of playing that character and people are so used to that character that you forget the character’s history. So there’s a lot of compelling stories to tell about someone who has a dark past."
Finally, the question was raised: After delivering Captain America: The Winter Soldier, Captain America: Civil War, and these two gargantuan Avengers movies, would the Russos finally be all Marvelled out. To which Anthony replied, "I mean, we haven't talked about doing anything beyond these movies simply because we still have a mountain to climb with these two films... but we would certainly be open to working with them."
Avengers: Infinity War is out May 4, 2018 -- just over three short months from now -- while the spoilery-titled Avengers 4 is due out the following May.