On the 20th November, YAMAHA made an official announcement regarding VOCALOID 4's release. It was announced that the release would be in December 17th, 2014
According to Wikipedia, there are some products of V4:
VY1v4 was realeasd on December 17, 2014. This is the latest version of the VY1 product. It contains 4 voices("natural", "normal", "power" and "soft") and was released on December 17, 2014, for both PC and Mac.
|VY1v4 box art|
A female English vocal developed by VocaTone. Ruby was originally going to be due before Christmas of 2014, however, PowerFX confirmed that she would be postponed. So her status is still in Development.
Megurine Luka V4X
Megurine Luka V4 will be released on Februari 2015 as an update from Vocaloid 2 Megurine Luka. In January, it was mentioned that a "POWER" vocal was being produced. In late December, Wat mentioned that Luka was focused with variation of "breath", in contrast to the Kagamines strength of tension.
|Megurine Luka V4X|
Kagamine Rin/Len V4X
Kagamine V4X package will be released in the 3rd quarter of 2015. On November 21st, Wat shared that the Kagamines are going to be a V4X title, like Luka. At this time, they were testing and implementing E.V.E.C. on the duo VOCALOIDs. In late December 2014, Wat tweeted saying the new V4 update was about 35% complete. Wat also mentioned that they were aiming for variations of strength with their vocals and control the vocals force.
Yuzuki Yukari V4
Yuzuki V4 expected for release in quarter 1 of 2015 .On 20th December, via a livestream it was announced that Yukari would receive three V4 voicebanks. As well as her whisper "Onn" (穏) voicebank; a powerful "Lin" (凛) and a natural "Jun" (純) voicebank, similar to her original V3, would be released. It was also revealed that Yukari's voicebanks could be purchased together in one package or separately.
|Yuzuki Yukari V4|
Jun (Natural), Onn (Whisper), Lin (Power)
SF-A2 Miki V4
SF A2 Miki V4 as an update of Vocaloid 2 is stil on the Development. Miki was the first of the VOCALOID2 vocals to be announced for the updates. There is no information yet about when it will be released on 2015.
|SF-A2 Miki V4|
Kaai Yuki V4
It was later confirmed that due to Yuki's original voice provider maturing, possible growl samples would have to be recorded from a new voice provider.
|Kaai Yuki V4|
Hiyama Kiyoteru V4An update on the Vocaloid 2 product. There is no information yet about when it will be released.
|Hiyama Kiyoteru V4|
Nekomura Iroha V4An update on the Vocaloid 2 product. There is no information yet about when it will be released.
|Nekomura Iroha V4|
Sources: Wikipedia, Vocaloid Wiki, Official Vocaloid Art