SEGA releases almost one Yakuza game each year now, right?
As it stands, Sega expects three PS4 SKUs for this fiscal year.
Alien: Isolation covers two of them (US and Europe release), so either they're also releasing it in Japan, or they have an additional PS4 Japan-only title.
It's possible they will do something like port Diva F 2 to PS4 or have a Yakuza game ready, though I'm kind of not expecting the next Yakuza until Fall 2015.