Nearly all major movies have pick-ups, ie returning to do some minor principal photography (adding a few extra shots to existing scenes, maybe a few minor scenes) to add stuff that they see is missing only when they do the first edit. That's a long way from reshoots, where they rework the actual storyline or tone of…

James Gunn has already gone on record that he wants to keep Peter Quill as the only Terran human in GotG, which would rule that movie out.