Interestingly, he also predicts that more than 50% of Neo sales will be for the A321.
What Leahy actually said is that over 50% of the
production (not sales) will be for A321s.
Essentially, Airbus will be prioritizing A321 deliveries over the rest of the A320 family. And why not -- when you have a clear market advantage, it's in your best interest to move as quickly as possible to fill it -- before your competitor across the pond can respond (e.g. with a MAX 10).
From a
sales perspective, the A320neo accounts for roughly 70% of the orders vs. 30% for the A321, plus a few A319s. I don't see this split changing significantly considering where we are in the industry's order cycle.