In SBS One Piece Volume 97 someone asked Oda about his claim that the whole One Piece series would end in 5 years.
Question: Odacchi! Is it true that One Piece will end in 5 years? Even if that’s the case, a public statement like that is really vexing for the fans! Many friends of mine who are fans burst into tears with this sudden announcement! I feel like shouting “How could you do this to us!?”, but I don’t want to stress you out. (P.N.: pari_bentham)
Oda: By “ending”, I mean the juiciest part of Luffy’s adventure. Since that’s when the mystery of “what is the One Piece?” is to be revealed.
Right now Wano is heating up, if Luffy is able to leave here in one piece, we’ll get to a development that will engulf the entire world, the likes of which no one has read before – the greatest war in One Piece history.
I said what I said so that the reader’s hearts would be prepared, since it’ll be such a long arc, and one that will really pin things towards the finish line.
That being said, I’m really enjoying righting Wano right now, and am pumped to finishing it!
So Oda more or less admitted that the plot will continue after One Piece is found. Teach would have already been beaten by Luffy at being Pirate King. And what else is there to do besides take on Im-sama?