I'm surprised by the upper range of some of the reactions in here.
Potentially, yes, this could be something big. Yakuza is a moderate-sized franchise in Japan which has been PS3-exclusive so far.
But for the time being, we should just treat what it appears to be. An attempt to gauge the fanbase interest on a certain platform as we transition into the next generation. Not a very good one at that (since it's a port of a port). This'll struggle to reach any semblance of decent numbers.
I could see Yakuza going multi-plat with Wii-U next gen just as an attempt to expand the audience. They've been sitting on the same ~ 630k fans the entire 7th generation. An exclusive Wii-U version seems out of the question, although stranger things have happened.
But just as I don't expect Ninja Gaiden; Tekken or Warriors Orochi etc. to go Wii-U exclusive simply because an earlier entry was ported to the console; I would apply the same logic here.