Burning Blood 2 will probably expand its roster to include canon Dressrosa (In PW3 it was half filler since the manga was still going) and Zou arc. I predict Kaido, Jack, and some Minks to make it to the game.
Tbh I wouldn't want them to add characters we still don't know anything about (in terms of fighting). Let's take a look at Shanks for example. He hasn't been shown fighting so far in the Manga or Anime and yet he appears in a fighting game wherein the character's use their "signature moves" - even though he hasn't shown any moves at all.. But I guess it's all up to Bandai to decide what sells best :D