As fine an aircraft as I believe the 319 to be, I honestly cannot see it winning this battle. Low fares airlines succeed because they cut costs to the bone; adding a new aircraft type, with all the training, spares, infrastructure etc. would undermine EZY in its battle against low cost carriers, all of which (exc. Buzz) rely on 737s; I'm not saying the 319 will never make it as a low cost acft, but for whatever reason, the 737 has - be it in Brazil, Canada, Australia or Europe - been the chosen instrument for low cost airlines. EZY has built its success, a proven formula, on the 737, so why change horses now?
That said, I'm sure Airbus recognises very well that it needs to get the 319 into the low cost market and I am sure the market will throw up further chances, perhaps in the guise of a new carrier, but it's not going to help AI's chances with EZY.