According to an article at today's opening performance of Shounentachi in Tokyo it was announced that there was a good chance that A.B.C.-Z will be going major next year as a seven member group called A.B.C.-xyZ. the added 'xy' will be for new member(s) that are being called 'sexy tantou' which I'm not sure how that translates into English, maybe 'in charge of sexiness'?
Nikkan Sports article. (Japanese)
I really don't know what to make of this announcement and I hope we get some more information about it soon. Or at least someone will translate the full article as I can only get so much from it with my limited knowledge of Japanese.
EDIT: Okay, I did a search of blogs to try to get more information and I think I may have found who one of the new members of the new group will be, Kikuchi Fuma. One blog listed him and when I did a check of who was in Shounentachi on Johnny's net he's listed at the bottom as a special guest so it is plausible. This is going to break the hearts of B.I. Shadow if it's really true.