Fans were excited when Ayesha, the Golden High Priestess of the Sovereign mentioned "Adam" in GOTG 2 which refers to Adam Warlock, would be appearing in the Guardians of the Galaxy Vol. 3. Unfortunately, James Gunn never confirmed Warlock would appear in the movie.
"I never said Adam Warlock was in the movie," Gunn clarified.
Christopher Markus, writer and producer of Avengers: Endgame revealed in an interview,"We didn't introduce Adam Warlock, because it's a massive backbend and you practically have to make an Adam Warlock movie to introduce him.He just can't walk onscreen. So, there was a brief moment where we were like, Ehhh..., and then we were like-- [He points to the movie's poster.] We have that many characters already! And then there were others we couldn't use. Like, Silver Surfer would have been useful, but we can't touch him. Currently."
Guardians of the Galaxy Vol. 3 is expected to be released on 2022.