It seems that the incentive for fairly specialized sub-fleets is smaller than the possible economies of scale coming from operating identical aircraft across the board and more importantly, than the incentive for the OEMs to maximize the output of existing models while avoiding investments in new models. As a result, the gate size hasn't really been so far a serious constrain for the NB, since there hasn't been any clean sheet design that would have been constrained by this limit. Nevertheless, it appears that the gate constrains will be dealt with by means of folding wingtips on the expected clean sheet designs.
This being said, with the progress of automation, sensors and AI, I'm wondering if the way forward couldn't be reduced gates and taxi clearances rather than adding the weight and the complexity of folding wingtips. Any stupid car will soon look much smarter than the most advanced airliners when it comes to taxiing and parking.
I also tend to believe that folding wingtips is not the way forward. Wind turbine manufacturer Enercon tried blades which were divided in two for better transport.
E.g. E141: 16,2 m inner blade section, 50,5 m outer blade section. The turbines with divided blades were discontinued after a short time. However to install a huge wind turbine at a remote place may have more logistic problems beside the blades. Maybe other components were too expensive?
However later designs of theirs were full blade again. I'm not aware any other wind turbine manufacturer tried divided blades. So I believe divided blades are rather not cost effective.
"the incentives for OEMs..."
The supply chain can't keep up anyway. However it will not be forever a seller's market. I hope once offer and demand balances the OEMs will ask what are the appropriate designs for the available technology.
Why they didn't do it 20 years ago? I assume
a) it was more important to focus on wide-bodies / twins with good range at reasonable capacity
b) airport infrastructure was unsuitable for a 45 m wing narrow-body. Which brings us back to the chicken and egg problem.
Why are turboprops so economical? Because they push a lot of air with medium speed as opposed to less air at high speed.
There seems to be a majority opinion on a.net that the B737 MAX is limited by the space under the wings. While it is true for high MTOW versions, is it true for the vast majority of narrow-bodies? Let's assume Boeing's software will be fine once they provide redundancy.
CFM 56-5B series (A 320 family): Bypass ratio 5,5-6,0 / Overall pressure ratio 32,6 - 35,4 : 1
CFM 56-7 series (B737NG family): Bypass ratio 5,1-5,5 / Overall pressure ratio 32,7 : 1
IAE V2500 (A321) : Bypass ratio 4,5:1 / Overall pressure ratio 35:1
Leap 1A (for A320 Neo family): Bypass ratio 11:1 / Overall pressure ratio: 40:1
Leap 1B (for B737 Max family): Bypass ratio 9:1 / " : 40:1
PW1100G (for A320 family): Bypass ratio: 12,5:1 / Overall pressure ratio: ?
Why can the A320 Neo not profit (or profit more) from it’s bigger engine diameter at common MTOWs?