As we know already, four J-Pop/Anime licensed songs will be removed from Sorairo next Tuesday. As such, the Q&A corner in the official website has added a reminder of the song removal. But don't you notice something more here?
According to the second paragraph, another four more songs are affected: Natsu Matsuri, Tentai Kansoku, TRAIN-TRAIN and Super Mario Bros, all of which are staples of the series. They will be playable in Sorairo and the future December firmware update (removing any one of these four songs would raise a LOT of eyebrows), but if for some reason a cabinet is still using the original Taiko 0 or Katsu-Don, these four songs will be deleted; probably to encourage arcade operators to upgrade the HDD.
Thanks to tetsutaro for the find!