James Gunn has finished the first draft of the screenplay to Guardians of the Galaxy 2. This comes only two months after he submitted a treatment to Marvel Studios. How could he finish the first draft to the screenplay so quickly? Perhaps it was not going to be all that difficult after having written a treatment that was 70 pages. The number of pages is double the length of the traditional treatment. Maybe Gunn had a lot more material already written out in great detail. Or maybe Gunn has a really epic idea in mind for the sequel.
Andy Wirth says that at present, no one knows what the sequel is going to entail. Unlike D.C. Comics, Marvel has a tendency to better preserve the secrecy of their material. Finding out the details of the new Guardians movie is not going to be easy, although details are surely going to leak at some point. One reason it is hard to predict what is going to occur is a lot of changes have to be made from the source comic book material.
The heroes owned by Marvel Studios are mostly of the earthbound variety. The superheroes the Guardians meet in the comic books are currently owned by Fox. Since Marvel Studios and 20th Century Fox do not have any agreements in place to share characters, Gunn has to come up with more original material. Marvel might not entirely like that, but no other real choice exists.