10 Most Believable Avengers 4 Fan Theories
6. Gamora Escapes The Soul World... And Undoes Thanos
The Theory
As the Russos hinted that Gamora is trapped in the Soul World, it makes sense that we're going to see more of her in Avengers 4. And once Peter Quill gets wind of her being trapped, there's no way he's not going to try and rescue her somehow (assuming he's brought back to life before her).
One theory suggests that the "love sacrifice" clause in the Soul Stone's contract was no more than a trick and that Gamora is now one with the Stone and will bring about his demise. That would suggest she'd have to escape her ethereal prison first, of course.
Why It's Believable
It might be misdirection, but there's already been a couple of hints that Gamora appears in both Avengers 4 and Guardians Of The Galaxy Vol 3, which will be remarkably hard if she is fully, really dead.
And the idea of Soul World being an actual location is very much lifted out of the comics. It wouldn't be at all surprising to see her scheming an escape just as she escaped Thanos in the first place.