Oda's hinted at major manga events a few times outside of the chapters, though. Back when the Water 7 arc was running he had hinted that a crewmate would die (which later turned out to be Merry). He actually revealed a rough sketch of Jinbei before he physically appeared in the Impel Down arc. And of course, the most recent hint he gave was the one about the current arc being Luffy's last adventure at 17. And again, he already kind of gave a hint that Luffy would at least have a NW ally who was a former enemy.....
But y'know, considering the latest spoilers that appeared, I wonder how many people will be clamoring for Bonney to join the crew?
