Imo Oda has showcased Seiryu DF performance to the limit, so the fruit wont be used again. On the contrary, BM's DF is underutilized imo, it has a bigger chance to be taken as BB crew's fruit...or even BB himself? So "Luffy vs BM" and "Luffy vs WB" (the rest of Rocks' crew" will also manifest in the form of Luffy vs BB. Just thinking about this recently.