In the end I have chosen to speak to Sandman (who's japanese) directly.
He has told me that the editor Iwasaki says " そのときが次の…ジャンプの次の号くらいじゃないですか" which translated would be " The chapter you are talking about will be included in the ... next, next Jump right? "
As I said in my previous message, Iwasaki does say the word " next " twice in a row and that's why some people who know Japanese but are not Japanese understand that they mean chapter 987. But both Sandman and other 5ch Japanese understand for the context that the editors talk about the next Jump and if so, they talk about chapter 986.