We've been hearing rumors about Captain Marvel appearing in the MCU for a few years now. We've been hearing that she may debut in Avengers: Age of Ultron, but if she doesn't we'd love to see her in Guardians of the Galaxy 2. A bit of character juggling would have to be done in order for it to fully make sense, but Gunn has shown that the source material is more of a template and guideline than actual doctrine. There have been several versions of Captain Marvel (aka Ms. Marvel) in the books, the most popular of which is Carol Danvers. However, there isa cosmic Captain Marvel, Phyla-Vell, who recently joined the Guardians in the comics. Her origin has ties to both humanity and the Kree, so if Gunn doesdecide to explore more of the Kree storylines in his sequel, one could easily see a way to bring Ms. Marvel into the mix, then give her her own, well-deserved spin-off.