Even Japan doesn't give a shit about that banner.
One Piece
John Hernandez
Brayden Watson
No, the 80% thing is relatively recent (2018), just google it. You shouldn't take it too seriously though, WCI was ~25 chapters longer than Oda assumed around chapter 850.
Carter Morales
He said 80% done which meant there's roughly 5 years left
Isaac Ramirez
Doesn't matter, it'll be very likely much longer, he just say that to make the upcoming arcs more exciting but OP will stay for like 6-8 years more