User blog comment:Ryuzakiforever/Pirate Warriors 3 Checklist/@comment-9022101-20150212223028/@comment-972068-20150213232314

As I said before, these games are going the DBZ route. By the time PW4 comes out, a few more key characters will be added, which probably will be Mr. 3.

For a more direct example, it wasn't until DBZ: Budokai Tenkaichi (which is kind of the fourth game) for all of the Ginyu Force to be added. In Budokai 1-3, it was just Ginyu and Recoome.