They're with the largest agency in the country - so the stats are probably good.
However, the stats will be somewhat screwed because any agency that has managed bands will push those bands when asked for a recommendation from a client, at which point, it doesn't really what the lineup is. Unless the client really wants a mixed gender band, they'll tend to go with what the agency pushes, so the lineup becomes less important. In reality, as long as the client likes the sound of the singer/singers, then you are good.
This is where changing the singer could be a problem as all the promo features the current bloke.
I already know what's going to happen. As the clients see the videos (both old and new), they'll say, we want the band with the old singer, who is still in the band, to sing.