It wouldn't be like PS3 to Wii, it would be easier to port down too.
Devs already have problems "up-porting" to Wii U from PS3/360.
I wouldn't want to imagine downporting to Wii U from PS4, given that Yakuza traditionally relies heavily on large storage and harddrive use, and I figure Nagoshi will go HAM on dat 8GB GDDR5.
Yes, I know the Wii U has 25GB discs and internal storage, but eh.