User blog comment:420pirate/The Shadow Shichibukai/@comment-4754162-20120320101326

Could be that as you have said, or it could be a gimmick of how he uses shadows to disappear (kinda like teleporting) to a short distance away - enough to get away from Doflamingo. And sounds legit that he may reappear in NW arc but not in major role... kinda like Mr. 2 reappearing in Impel Down arc, not in a major role but quite important nonetheless.