The Marvel Cinematic Universe has teased the Young Avengers ever since Phase 4 started, with the likes of Ms. Marvel and Kate Bishop all having played prominent roles in the MCU since. As more and more of the fledgling superhero team joined the MCU, many expected them to team up together to form their own squad.

In the comic books, this team is called the Young Avengers, and with the introduction of Cassie Lang in Ant-Man and the Wasp: Quantumania, there's enough of the youngsters in the MCU right now to form a legitimate lineup, especially with the absence of the original Avengers team.
Unfortunately, as per Ant-Man 3 producer, Stephen Broussard, Marvel Studios has no plans for Young Avengers, saying:
There are no current plans for that. A lot of Phase Four was about introducing the next generation and introducing new characters. I think that's one of the themes that the next generation reminds us, and that would be exciting to explore with Cassie going forward, or with any of the new characters, like Kate Bishop. People like that, who have inherited the mantle, and keeping to fight the fight, and make the world a better place.
Of course, just because it's not in development, doesn't mean it's never going to happen. The fourth phase of the MCU was just as much about introducing potential Young Avengers members as it was about picking up the pieces after Earth's war against Thanos.
Now that the Earth's mightiest defenders are no longer, no one is there to stop someone like Thanos, or in this phase Kang, which is said to be an even bigger threat than the Mad Titan.
Phase 5 will finally give the MCU a threat worth working together to fight against, which is probably why it's rumored that Captain America 4 will see the formation of the new Avengers team.
With at least two other teams, in the Fantastic Four and the X-Men, all set to make their MCU debuts sooner than later, the MCU isn't in any rush to send young superheroes off on their own.
At this point, it's highly unlikely that we'll see the Young Avengers formally make their debut in the MCU until after Kang is taken care of (or is it the Beyonder?).
For now, fans can look forward to watching Cassie Lang prove herself in Ant-Man and the Wasp: Quantumania on February 17.