I mean if you think about it, this group has been with us... 8 years now? They haven't had a change in line up since 2005 when Maiha left... and the members are almost "Up there in years" and almost "too old" to be idols...I know it's a little early to talk about this but the ages of them are kind of "older" for idols.
Shimizu Saki (清水 佐紀) November 22, 1991 (age 20)
Tsugunaga Momoko (嗣永 桃子) March 6, 1992 (age 20)
Tokunaga Chinami (徳永 千奈美) May 22, 1992 (age 19)
Sudou Maasa (須藤茉麻) July 3, 1992 (age 19)
Natsuyaki Miyabi (夏焼 雅) August 25, 1992 (age 19)
Kumai Yurina (熊井 友理奈) August 3, 1993 (age 18)
Sugaya Risako (菅谷 梨沙子) April 4, 1994 (age 18)
with the youngest member being 18, I think some changes might come. Either a member or two will leave (Like Captain or Sudou - My gut kinda hits me with them), new members will be added (which I find unlikely), or the group will disband within the next 5 years (which I find possible.)
Takahashi Ai left morning musume at the age of 25 (September 14, 1986 (age 25)) which is older for an idol and Niigaki is leaving us at the age of 23 (October 20, 1988 (age 23)).
I don't know what you girls might think, but I don't think berryz will be a group anymore in 5 years, if they are i of course will be happy, but extremely surprised.