It seems very obvious to me that they intentionally dropped the Zodiac in gen 9, simply because there were so few left that it would have gotten too predictable as to what the fire starter was going to be. Maybe they'll throw us a curveball and do it one more time in a gen down the line, but I don't expect it to happen more than once if that. You'd have to be a big coper to deny it from gen 1-8 though.