It would've been cool if there was a Yakuza set in early Showa period Japan, in the 40s or 30s. Like if it has the vibes and atmosphere of old Yakuza movies like Drunken Angel, run down and dirty slums.
It will probably happen somewhere down the road, I just hope the protagonist is not "NotKiryuKazuma", and actually some entirely new character with distinct personality and looks.