User blog comment:Ghmorello/Chapter 919: Gotta Get Back! Back To The Past!/@comment-28995593-20180928063504/@comment-2600:6C5D:5D00:1C9:C542:63AC:809C:51F2-20180929012426

I think Madam Sharley's prediction was misinterpretted. What if it means that Fishman Island will fall to ruin but is saved by Luffy. The pirates may not be able to open the borders, but Oden may be able to due to those sheathes the teacher was referring to. Oden did commit a taboo of Wano for leaving its borders to be a pirate and he is on of the daimyos.