How many characters are we thinking? Around about 15? Maybe more. I haven't played many of their games, but Arc Systems are all about the systems and making every character play differently. I'm not sure how you could do that with Dragon Ball since with a few exceptions (ie Buu) they're all kind of...the samey. Different projectiles and supers, but I'm not sure what else.
Since we got Trunks confirmation, I figure Piccolo is the next logical step. After that, I figure we'll get at least one other version of Buu, Goten, kid Trunks (and by extension Gotenks, as well as the other fusions), adult Gohan/Saiyaman, Krillin, Broly, and/or Beerus. Maybe some other movie villains, or some Super representation like Hit, Goku Black or Zamasu.
Since we got Trunks confirmation, I figure Piccolo is the next logical step. After that, I figure we'll get at least one other version of Buu, Goten, kid Trunks (and by extension Gotenks, as well as the other fusions), adult Gohan/Saiyaman, Krillin, Broly, and/or Beerus. Maybe some other movie villains, or some Super representation like Hit, Goku Black or Zamasu.