Well the latest volume to be release come July 2012 will be Vol 12 and with another 14 new plus 1 Secret for your collections. With the annoncement of the line-up comes also the Full reveal of all the 14 Rider Masked except the secret.
As shown from the photo below, there will be Rider Masked from 8 difference series with the breakdown as follows:
AGITO X3 = Agito Burning Form / Another Agito / Gills
HIBIKI X1 = Rider Eiki
THE NEXT X2 = Rider 1 / Shocker Rider
KIVA X1 = Rider Arc
DEN-O X1 = Goludora
W (Double) X1 = Accel Booster
OOO X2 = Shouta Combo / Putotera Combo
FOURZE X3 = Base State / Meteor / Cosmic State
W (Double) Secret X1 = NAZCA DOPANT
Release date is just right the corner, dun miss it.