That "soon" is something I have been reading for years, and something in what I had faith too, but it's been 2 albums, 2 mini albums, and 12 singles, and there's no improve because people already knows what do they have to offer to them. About the wota thing... you can appreciate it on album releases. Like I said, a casual fans waits for an album to be released and this is why album sales always > single sales. This does not happen with Berryz, showing their fanbase is closed at all. I even think they don't want to expand it. UFA is happy doing 20K for each single but like MoMusu sales went downhill because yes, even wotas lose interest, one of these days it might happen to Berryz, and by then, adding someone will be useless; but adding someone now might make people get interest in a future third album and give them the definitive push they need. Just what I think :p
Their sales don't seem to be dropping, so they could still "soon" have a big hit which really puts them on the map, and I don't think they need a new girl to do that. Solid sales are better than dropping sales.
Remember that Berryz only debuted in 2004, and the arrival of Maki was in 1999. The addition of a girl was successful then but remember 6th gen? As much as I love them, they did nothing for the sales or popularity of Musume. Times have changed.
I still believe "soon" they could make it big, simply because in a few years time, they would all be a little older, meaning they would all be even better at what they do than they are now. They soon may just have
that song, like special generation.
Berryz have been around for 2 years, Morning Musume have been around for 10, and Berryz are having to cope with the reality of the internet, when back when Maki joined, people would buy the single out of intrest. With Berryz, people might download the single out of intrest, doesn't effect their sales.
Overall, I just think it's still too early to give up hope with Berryz.