Jennifer Walters is joining the MCU in She-Hulk, and the Disney+ Marvel series is completing Phase 4's original Avengers replacement. She-Hulk is yet another step by Marvel Studios in the mission of expanding the MCU through the Disney+ platform, a strategy that so far is proving successful. Fourteen years after Iron Man, the She-Hulk trailer proves that there are still dozens of Marvel characters and storylines that have yet to debut or have a proper role in the MCU, and that shows how exciting the future of the franchise is.
With the MCU's next Avengers: Endgame teamup likely a few years away, the franchise has the opportunity to introduce new names and lay out future storylines without having to worry about an urgent, imminent threat. This has enabled the MCU's Phase 4 projects to have more distinct tones, such as WandaVision's wacky, surrealist journey, What If...?'s not-so-episodic exploration of the multiverse, and now She-Hulk's comedy law drama. The wait for Avengers 5, while unpleasant, is necessary, but it will be a fascinating lineup when it comes.
Besides exploring these different tones and formats, Phase 4 is clearly working as a moment of transition for the MCU in terms of established heroes passing the torch to the next ones. Ever since Endgame, all of the remaining original MCU Avengers plus other well-known MCU heroes have been seen either mentoring or passing their mantles onto a younger, rising character. Black Widow had one final mission with Yelena Belova, Sam Wilson left his Falcon gear to Joaquín Torres before becoming Captain America, with the shield passed to him by Steve Rogers, Hawkeye mentored Kate Bishop, and Thor will soon be working with Jane Foster's Mighty Thor. Hulk training She-Hulk is now the latest example of how the heroes the MCU has been following for the last decade and a half are helping the next generation of characters to take their place in the spotlight. Even heroes that only joined the Avengers at a later point, such as Doctor Strange and Captain Marvel, are already receiving apprentices or legacy partners, as seen with America Chavez in Doctor Strange in the Multiverse of Madness and Kamala Khan in Ms. Marvel.
A Young Avengers movie or TV show happening in the future is likely, but that is not the only reason that the young, legacy characters are joining the MCU. Unlike the comics, the live-action movie franchise can only center around the same big characters as the original Avengers for so long; actors age and contracts expire. Getting an actor to reprise their MCU role for more than a decade is difficult. Recasting a beloved character like Tony Stark or Natasha Romanoff would both be an almost impossible task. So it's important to have legacy heroes that can carry on the franchise. More than that, with Thanos and the Infinity Stones storyline behind the MCU, the many Marvel characters that did not get to appear in the Infinity Saga can now finally be incorporated into the franchise, either as pillar members of the Avengers 5' lineup of heroes or as recurring faces in other projects.
The original Avengers have already performed remarkable feats in the MCU history, most notably defeating Thanos and saving the entire universe. Many of them are now gone, and for those who are still living, it's time for them to rest. However, Earth will not lose its Mightiest Heroes as new names like She-Hulk's Jennifer Walters are already being mentored and trained as replacements. By the time Avengers 5 and other team-up movies happen, the MCU's roster of characters will be quite different, but no less prepared.
