Sega has updated the official site for the Yakuza series with a video showing all of the events going through the 4th installment with a teasing message at the end. After recapping the events from Yakuza 4, the video shows the message “And then…” followed by “First look on May 24.”
I think it is safe to assume that this reveal will center around Yakuza 5, which was announced last year but was not given any details. The last game that was released in the series was Yakuza: Dead Souls which is not considered a cannon piece of the story.