Found from the official site by crystalsuicune. Hang on, wasn't Namco supposed to tell us this tomorrow on the blog?
Six songs as usual, two J-Pop, two Anime, and two Namco Original. We all know the classic TRAIN-TRAIN, and Aruite Ikou is another new Ikimono Gakari song. Oshiri Kajiri Mushi is from the TV show Minna no Uta and this is its first console appearance since DS2 (really easy song), while Tomare! should excite the more hardcore anime fans. It's not Hare Hare Yukai, but it's still good.
And on the Namco Original side, Crane City is being given for free (we last saw this song being hinted at on the .EDAT files from last month's downloadables) and a new song, Kurukuru Kurokkuru, whatever that is. Lot of weird and wonderful new names they're coming up with.
Available for download starting tomorrow, on the 10th of May.