One of the new songs in Hatsune Miku: Project Diva Ver. 2.5 is “Spica 39’s Giving Day Edition” by Toku. Sega released a video of the song in the game a few hours ago. The video states that Ver. 2.5 will have a lot of new songs and is slated for an autumn release in Japan.
A few other new songs have been confirmed for Project Diva Ver. 2.5 as well, which you can read about here, along with some of the new modules in the game.