In Japan, reaching 20 years old(Hatachi) is considered adulthood and, believe it or not, ALL members are 20+ years old now(Risako just turned 20 this year). Not only that, but they've also spent their entire childhoods in the spotlight and it would be selfish for us to ask for more. I've been a fan since 2008 and they've accomplished so much since I discovered them. I was even fortunate enough to attend their concert in Bangkok.
The fact that they considered disbanding tells me that this is the end of the road for the group, regardless if they officially graduate or not. Unlike Morning Musume, which has been around so long with a perpetual cycle of new members, Berryz Kobo(and also C-ute) have not added new members since their debut. We all saw what happened when MM went nearly 6 years without adding members and the huge age gap that followed. A few years ago would have been a good time to add new members and "seed" the future of the group, but that didn't happen. Personally, I'm more than content with an "indefinite hiatus" because it would be hard to picture Berryz Kobo with new faces or without old ones.
Sure, we can hope for a reunion in the future, but I wouldn't count on a full-fledged comeback unless they comeback years later after getting married/having children/etc. That would be quite awkward. In the meantime, I'm sure they'll still be in the spotlight as with some graduated/former H!P members. All we can do now is support them for their last months of activity and for the rest of their post-Berryz lives.