With Ego being completely absent from the marketing to this point, it is difficult to determine what exactly his role will be, and if a potentially antagonistic relationship between him and the Guardians could emerge.
With that in mind, a villainous turn for Ego could be an interesting development for the story.
So far, Elizabeth Debicki’s Ayesha and her Sovereign race have been sold as the primary villains in the Guardians of the Galaxy movie sequel, along with a new faction of Ravagers.
That said, a potentially-wrecked relationship with his father could ultimately help drive Star-Lord back to Earth, just in time for Avengers: Infinity War.