Without Kojima and/or a substantial investment in new dialogue/cutscenes I don't see this happening, and I don't see Konami throwing that kind of money into MGSV at this point. Kojima definitely isn't coming back, considering he's down the rabbit hole on Death Stranding right now.
And while "Kingdom of the Flies" being playable and intact would be nice, the game really needs a proper Act 2 to fix it's issues.
Not to mention I think someone would have noticed if Kiefer had been called in for more voice recording, which would be all but required to pull this off.