As I replied above:
"The existence of the XLR on new point to point routes does not mean that 100% of those seats are creating new demand out of thin air. It will create some new demand, however the vast majority will be offset by reduced demand on trunk routes via a 1 or 2 stop.
One airline putting XLR's on TATL routes (such as JetBlue) could mean another (such as Delta) needs fewer 330NEO's for its TATL trunk routes. X number of passengers need to be moved - if the XLR did not exist that lift would have had to come from somebody."
How many 330NEOs did DL not order because JetBlue is flying to LHR?
That's a strawman argument. Economically, there is substitution. Students learn that in microeconomics 101. Just because JetBlue is small relative to DL's Atlantic JV doesn't mean there's no effect. Imagine WIZZ, Ryanair, EasyJet, Spirit and others joined.
This is the point at which speculation marketing and economic theory meets objective reality.
Neither of you are wrong here.
In theory the A321XLR could be eating eating into the A330neos market resulting in it not getting orders.
However in a real world case like the Heathrow example it most likely hasn't had any effect on Delta's fleet planning.
It's a bit like the 787 hub and spoke/p2p arguments.
Back to MOM talk. It's interesting that you bring up EasyJet and Wizz etc. Most of the MOM talk other the years has been centered around Delta and United and a 757 replacement. But what about the potential for airlines that never had those. (I know Easyjet briefly had 757s)
Right now FR and Wizz etc all operate a single fleet type.
Thats a key part of their business plan, however they like many fscs are upgauging to larger aircraft.
Demand is still growing, sooner or later they'd require an aircraft larger than an A321/737?
Of course they could and another frequency, however airport constraints apply to them aswell and that may not always be a viable option.
Not saying that FR are going to upgauge to Dreamliners that's far too much for them.
But they'll need something bigger like a 762 but optimised for low costs.
It wouldn't be something that they'd be looking to purchase now. But when the 737 and A320s need to be replaced and if the NMA has the same type rating as their replacements. They could very well go for it.
There are also lcc airlines such as Pegasus. Unlike Ryanair and Easyjet they carry a lot of hold luggage and cargo.
It's a very tight squeeze getting that onboard so they'd be very interested in a wIdebody MOM.
A widebody doesn't have to have the same economics as a narrowbody. Thats just not how phsyics really works. The aircraft just needs to be viable within their business model.