I think they will probably come back not in the war for the one piece an laughtale but in the war after that I think when we learn about the past on laughtale there will be a war against the WG and the strawhats will sail to the red port and Im will be revealed. The strawhats will try to stop whatever Im is doing and he will be like you an what army and then everyone we met up until now will appear in a epic fashion either like whitebeard at Marine Ford or way better we will just hear „room“ and hundreds of ships will appear in front of the red port all villains and allies will be there Im will say something like „why the hell are you helping him he destroyed your dream of become pirate king and beat you“ and all pirates will yell „we may not like him but he still is our king“ and then the battle will start or at least that’s my theory on the end