On the 25th.
But this songlist, as a person who owns all three Wii Taikos, leaves a bitter taste in my mouth, even with the few new songs I get to play on it........I don't know what Namco were thinking, including Kikyoku and Numujika when they could be putting in Tanpou and AC00, among other jerkass choices....The only thing this POS is good for is using the Guide Mode to FC the four (five/six/whatever) god songs that are on it.
The Japanese may be praising Wii4 for having tons of high difficulty songs, but I'm not as impressed as I was last year, even though I'm still buying Wii4 anyway. Knowing Namco, the next Taiko is most probably on PS3/Vita and will have all the Taiko 0 unlockables to give the giant middle finger straight back at Nintendo......

EDIT: Although, Taiko 0 has its own new Uras and so do we (Lightning Passion Ura, dance storm Ura, Hakuchou Ura) lol
EDIT2: Also, there is a Story Mode of some sort, explaining the credits scene and theme song unlock.