Kitamura Eri and CUL
Besides Kitamura Eri, there is Lia, a Japanese singer that famous as the singer of Air and Angel Beats! soundtrack that will be a voice provider for Vocaloid3.
The two characters that take Kitamura Eri's and Lia's voice will be developed by Internet Co. Ltd. And as additional info, it is also mentioned that the upgrade version of Megpoid (GUMI) by Nakajima Megumi will be released as Vocaloid3. Both YAMAHA and all Vocaloid developers hope that Vocaloid3 will be a successful product such as Hatsune Miku from Vocaloid2. Even YAHAMA already claimed that Vocaloid3 has the most realistic sound ever. Vocaloid3 itself will be released on 30th September this year.
This is the video...
Source: Kaori Nusantara & Miku Zen