My theory is they are going to add Yatta2 in the following months. In the box art they show All the characters so far, and even the new ones...Yet they save a spot for Doronjo's assist characters...But Doronjo is no where near them, Yatterman 01 is right behind them. Coincidence? i think not! Also Yatterman 2 could take longer due to being very similar to Yatta1 so I think they are taking precautions to make her as unique as possible. Furthermore maybe we will see a DLC of some sorts happen? The wii Shop channel is not equipped with the capabilities but they might soon start adapting wii games and release a update permitting DLC programs on the shop channel. These are all Ideas.

I don't know how solid it is, but they already stated that a new feature they are looking into (if not already completely developed) is DLC for the Wii. Something about SD cards and what not. 

Also, notice that "Locked" section on the website that has yet to reveal itself? Not to mention in the E3 (or it might have been the TGS not sure) they said they were going to add something special to Ultimate All-Stars that he thinks we are going to be happy and suprised about. Makes you wonder...

she might be in it check the jp site