I've been following OP weekly for a loooong time, even though I didn't follow spoilers until WCI, I've seen so many spoiler providers shut down/retire. As long as physical copies are still being sold, we'll get spoilers and early leaked chapter. It's just the nature of things until Shuiesha discontinues physical releases and switches to 100% digital. Which won't be happening anytime soon.
It's most likely 6 chapters, but from experience, the first chapter of the new year (Chapter 967 in this case) almost always leaks earlier that normal and we get it last day of December-ish. So probably 7.