It Sounds Like A 787-300 To Me

Quote coming from: 

5 Things Boeing's Management Wants You to Know

".. [W]e see route structures around the world continuing to evolve as general passenger traffic growth is occurring, in particular, new regional structures, point-to-point connectivity. That's in this 4,000 to 5,000 nautical mile range, airplanes that are in the 220 to 270 passenger range. That's the ballpark that we're looking at and discussing with customers."
-- Dennis Muilenberg

Boeing is going big with a NMA offering. The decision to build a NMA tween the 787 and the 737 has caved into other considerations such as:

Plant expansion and space availability.Technological fall forwards from prior programsRange announcement of 4,000-5,000 milesSeat Announcement from 220-270 units.Mature supply sources in place.

Boeing already has the infrastructure to build more 787 and does not have as much 737 site capacity for a NMA. It has a process in place for building all CFRP aircraft from its two sites in Everett, Wa and Charleston, SC. In fact, Charleston has more available acreage for plant expansion than Everett has on its books. In SC Boeing can buy more land where in Everett the land around its manufacturing footprint becomes more expensive and in shorter supply.

Boeing can't use all its hard gained technology in a NMA metal frame concept. The NMA is ripe for everything Dreamed of over the last 15 years and it will go CFRP on wings and body. In addition, the body design will change to an unconventional shape which is  perfect for CRFP shaping. Using older 737 Max building technology limits any future following advancements for a new type.

The former 787-300 range was set at about 3,300 miles. What Boeing has learned it can build a lighter frame going 4,000 to 5,000 miles on new technology engines. Additionally, it can connect 787 technology to a NMA better than connect the 737 Max technology going forward. Weight saving "All electric architecture" may be a selling point on the NMA. A core operating system from the 787 is more inline for a NMA than using a Max type system for a NMA.

The announced seat capacity of 220-270 suggest a dual aisle - 8 across profile. Something like a 2-4-2 would get Boeing to 220-270 passengers in a two class cabin or less. The eight across would alter the 787 hull diameter by a small increment, thus allowing NMA sections to be moved by the Dream Lifter. 

In fact Boeing has access to an abundance of 747's on the used market where it can expand its Dream Lifter Fleet by several without immense costs incurred. Charleston could build the NMA and 787-10 exclusively. Everett on the other hand would build the 787-8 and 787-9 exclusively.

Finally, the supply line would not be disrupted having only a few modifications to its requirements. A hull and wing building source would have to be identified. The engine maker may go to "the winner takes all", when awarding to only one engine maker, like the 737 has used over its years. 

The competition would be fierce among the Builders. GE, CFN, PW and Rolls are the names of the big players. Engine supplier competition is a fortunate problem offering builders a chance at a whole new engine type unlike any other. A locked in exclusive contract is what stock market values are all about. The NMA could sell 2,000 units in the first five years. This may disrupt both the single and dual aisle current stability at this time. Boeing is betting it will hurt Airbus as a whole, more than its Boeing family of aircraft.