Now oda has a thing that he does. When a crewmember joins the crew the chapter is named "The ((Blank)) Person", if they join in a manner such that they might have divided loyalties then they don't get the chapter title until they have resolved their issues.
So far, we have gotten
"The First Person" Which was zoro in chapter 6, basically right away.
"The Fourth Person" in which we got Sanji, chapter 68, 2 chapters after Kreig goes down.
"The Second Person" When Nami joins in chapter 94, one chapter after arlong, but over 70 chapters since she was introduced.
Now Usopp is the third person, Chopper is the 5th, and robin in the 6th. Obviously chopper isn't going the focus of this arc so he is not going to 100% join the crew, but Usopp and Robin are as this is the desicive
arc for them both.
The next chapter will most likely be the final stand of Rob lucchi against Luffy, there is a outside chance that it will go on one more chapter, but I am going to gamble that its only 1 chapter.
IF the pattern holds then the chapter name for 426 is going to be "The Sixth Person".
I am laying odds now that all the cards are on the table and will be taking bets. You can bet up to unborn children, but nothing past that.
Chapter 425 'Some Variation of Victory' 3:1
Chapter 425 'Some Variation of Hit/strike' 7:1
Chapter 426 'The Sixth Person' 2:1
Chapter 426 'Some Variation of Victory' 9:1
Chapter 427 'The Sixth Person' 9:1