The next Yakuza game is called Yakuza Zero

[Xxain]

kupomogli said:
I was right. Yakuza Zero Chance For Western Release is prequel to the first game.

http://www.siliconera.com/2014/08/26/yakuza-zero-takes-place-1988-direct-prequel-first-game/

To be fair, everybody guessed that. It may even based on a book written as a prequel to the series.