In retrospect, The Avengers appear almost antiquated. What was one of the most significant shifts in franchise filmmaking—a linked universe of blockbuster films—was little in comparison to how the MCU evolved. You only had five solo films—Iron Man, The Incredible Hulk, Iron Man 2, Thor, and Captain America: The Original Avenger—before bringing everyone together for a six-person team in The Avengers, which came out four years after the first Iron Man. The MCU is considerably larger now than it was in 2012, thus bringing “everyone” together is a huge job that will most certainly take more than four years if all the foundations built in Phase 4 are considered.
The Avengers 5 could happen around 2025 (four years after Phase 4 began with Black Widow), but during a conversation about the upcoming Shang-Chi and the Legend of the Ten Rings, Collider’s Steve Weintraub asked Marvel Studios president Kevin Feige about when the next team-up might happen, and he sounded far more circumspect about the prospect: “I believe we want a decent length of time after the endgame to begin a new saga, which is currently happening and has begun,” Feige stated.
“And then, like you did in Phase 1, you need time to construct that tale before you start bringing everyone together.” Keep in mind that the concept of collaboration has evolved significantly since Phase 1. The MCU characters were mostly kept to their own movies in Phases 1 and 2, but now crossovers are happening, with Scarlet Witch (Elizabeth Olsen) and Loki (Tom Hiddleston) slated to appear in Doctor Strange and the Multiverse of Madness, and Doctor Strange (Benedict Cumberbatch) appearing before that in Spider-Man: No Way Home.
To put it another way, if you want to see these characters interact, you don’t have to wait for a new Avengers film. Marvel is also likely aware that Avengers: Endgame was a difficult act to follow, so rather than trying to outdo it and falling short, it’s best to take a breather, reset, and allow fans to build anticipation for when a new band of Avengers will join together to face a new danger.