I don't see why they wont still be able to perform live. As I said, Meimi sounded great.
And in all fairness, Takechan has sounded much better previously, so maybe it was just that concert that she was off during, I dunno. I haven't gotten around to watching Mechaike yet. I didn't even realise S/mileage was on it, for all the chatter about Momoko. Maybe tomorrow.