According to excite anime, a new singer with Sony Music named Haruna Luna will be performing the 2nd Ending Theme of Fate/Zero (featured in the continuation of the anime this Spring), which will be composed by Yuki Kajiura!. The title of the song is not announced yet however.
Haruna Luna is also a model for the fashion magazine “KERA” (which often features Keiko of Kalafina/FJ too), and drew public attention as a finalist for the fourth Anime Song Grand Prix of Japan. Kajiura has reportedly praised her voice for its sense of presence. For more info, visit her official site, or her page on spacecraft.
Thanks to elcazador!