He cites JP Morgan with an observation that not all of the delivery slots for A320ceo's are filled for 2015 (2014 is full) and therefore it would be a good decision not to boost output further.
Let's have a look at the current number of open orders for the A320ceo as well as those of the B737NG.
Here is how the backlog of A320ceo's develops if there would not be any new sale nor any cancellations. Of course there are some "risk positions" in the backlog: Kingfisher, the remaining Delta (Northwest) and United order and Mandala come to mind...
As of May 1st, 2012, there were 2084 A320ceo and 1286 A320neo on firm order.