As far as onscreen roles are concerned, in the comics, Ghost (who is a guy) has crossed paths with Black Widow, so it’s possible she could show up in her solo film, but it seems more likely Ghost could fit in to one of the many Disney+ series that will fill out the MCU in Phase 4. Shows like The Falcon and the Winter Soldier or Hawkeye seem like good candidates. Maybe Ant-Man and the Wasp will get their own series. With the MCU expanding at an incredible rate, the future is wide open for Ghost to return and now it seems like she very well might.