Potential Spoilers For Ant-Man Follow
The release of Ant-Man into theaters brought Hank Pym, Scott Lang, and Janet Van Dyne to the Marvel Cinematic Universe as proper superheroes, but the post-credits scene tease has fans wondering when Evangeline Lilly's Hope Van Dyne is going to suit up and get into the action as the new Wasp.
"It's a good question, and it will certainly be in phase three. Where exactly in phase three I'm not sure, but it won't be in Civil War."
Feige goes on to say that Wasp was planned to appear in Captain America: Civil War early on, but as removed. The reason for Hope's removal is similar to why Captain Marvel's cameo was cut from Avengers: Age of Ultron:
"She was included in early versions of Civil War but there are so many characters in Civil War that we didn't want to do her a disservice, like she flies in, 'I've got the costume now', and she flies out. With Ant-Man, and I'm not saying that's what Ant-Man does in the movie, but we already know him, we've already seen him. We haven't seen her as Wasp and we don't want to rob the opportunity of seeing her in the outfit for at least almost the first time, and seeing her dynamic with Scott in a way it could play out, so we're saving it. But it's going to be in Phase three for sure."
So now it's just a matter of where and when. If not Civil War, I would say Wasp would best fit as an ally to Carol Danvers in Captain Marvel. Avengers: Infinity War is another option, but those films will likely have an ensemble cast to rival Civil War's, so waiting would until then would almost defeat the purpose.
Ant-Man is now playing in theaters.