I think Reina is by far the best singer in the group, and while the noobs may be promising, right now they (obviously and understandably) lack a lot of polish and practice. No need to be alarmed, really, they'll improve.
I really don't understand people that say Risa can't sing or can't carry the group. Do It Now was one of the first videos of them I saw and I immediately noticed Gaki singing so well during her solo. That was close to her debut too.
I don't think that most people here are saying that she can't sing. It's more of a contention as to whether the rest of the group can do fine without her.
Well, some people are saying Mizuki can sing in this thread, which I would disagree with. And it remains Gaki could take a lot of Taka's parts for lives and handle them decently, which is not the case of the other girls.
Plus, without Taka + Gaki, the average tone will be much higher.
Gaki isn't leaving until May - they will have a full spring tour with her. From summer Riho and Zukki at least will have improved tons. idek what people are worried about. What I'll miss is the deep voice that Gaki has - Kanon will do that in a while but she's still too young I think. Maybe next year. I still want her (along with... who?) to take the mains in Manpower sometime soon though.