Kate Bishop's possible return in Hawkeye. Jeremy Renner finally got the opportunity to star in a Marvel Cinematic Universe show of his own in Phase 4, but the Disney+ series did more than just highlight Clint Barton. Hawkeye brought Hailee Steinfeld to the MCU as Kate Bishop, and by the end of the season, it was inferred that the character would become the franchise's new Hawkeye.
Hawkeye's ending doesn't directly set up Kate Bishop's MCU future but rather leaves it open for multiple possibilities. Marvel Studios hasn't confirmed if that will include Hawkeye season 2, appearances in other Phase 4 movies and shows, or a combination of both. Speculation has run rampant that Steinfeld will return to the MCU sooner than later, though. It would make sense for her to be present in the Echo spinoff series, work with Yelena Belova (Florence Pugh), or even help form the Young Avengers. The latter has led to rumors about Kate Bishop appearing in Ant-Man 3, which might have been set up already.
Over the course of Hawkeye's six-episode story, Kate Bishop is trained by Clint Barton to become a better archer and the MCU's next Hawkeye. This includes introducing her to a variety of trick arrows that Clint created. Clint proves to be quite resourceful with these trick arrows, as he uses Stark technology to great effect. He also takes advantage of knowing Scott Lang to use Pym Particles for a custom Pym Arrow, which grows or shrinks any object it hits. Now that Kate is the MCU's Hawkeye and familiar with said Pym arrows, she could take a trip to San Francisco for more Pym Particles, resulting in an Ant-Man 3 appearance.
While a Pym arrow could be what brings Kate to meet Scott Lang, it stands to reason that she'd play a much bigger role in Ant-Man and the Wasp: Quantumania once she appeared. Steinfeld's portrayal of Kate Bishop has already made her a fan-favorite character. A small role in Ant-Man 3 is certainly possible, but that would seem like a missed opportunity. The Pym arrow should really only be a means to get Kate involved with the movie in an organic way, which then allows Marvel Studios to further set up Kate's MCU future.
It is no secret that Marvel Studios is building its Young Avengers team. Kate Bishop will be one of the main heroes featured, but Ant-Man 3 adds even more hype to the conversation with the inclusion of Cassie Lang. The MCU recast Cassie with Kathryn Newton stepping in for Ant-Man and the Wasp: Quantumania too, which signals the potentially important role she'll play going forward. Having Kate and Cassie interact here should be a priority for Marvel. It'd bring two Young Avengers together, at last, possibly making them the two leaders of the MCU's next superhero team. Now it's just up to Marvel Studios to payoff this potential Hawkeye setup.