I'm not too worried, because the interest in Young Ji and seeing the new dynamics of going back to 4 would be enough to sustain their momentum once the single is released. However, they really need to bring out something new right now, either with the song or the dance routine, because they've done virtually every concept there is in KPop, and if they just stick to being cute or sexy, they will go stale easily. 'Mister', 'Step', 'Lupin' and 'Pandora' all had long shelf lives, mostly because their sound is distinctly theirs. This time, though, they need that new song to be as different from the old repertoire as 'Rock U' is from 'Break It', otherwise that song will be measured by how it stacks up against those from the 5-member era. So thinking about it, bringing in a new composer was a smart move.