My assertion is not whether Boeing goes forward with 757 replacement? Research and statistics shows Boeing biffed it when it closed off the 757 without having an answer. Hence the long and perilous journey with the 787 program. The 787 is no longer the center for development stage, but has matured forward ushering the production and marketing phase of its future legacy.
The MoM, aka: Middle of the Market for range, size and aisles has arrived. Long ago like last January, Winging It proposed a seven across dual aisle 15 foot wide body for the MoM. Featuring carbon fiber wings and re-engined (up for bid maker) engines for rigorous and efficient duty. A Winging IT diagram was even offered for visual effect. It’s also has been noted the seat range will become a 200-270 seat cab. The single aisle is out, if it goes for 270 capacity. It will not need a cattle shoot down the middle it will need a fork in the path to the Jet way with dual aisle control for all cattle in economy.
Read this then you decide:
The Winging IT case was made at seven across, dual aisle with about 210+ seats going forward. Boeing will cut its seat count down to 250, because it’s a round number and a MoM appropriately configured could do 250 without having passenger contortion confronting its product. Any customer optioning of going gonzo on the seat count should receive a void for any Boeing guarantees for its aircraft where the customer airline must stay within original engineering constraints for space and comfort. If Boeing says it’s guaranteed to travel up to 250 passengers then so be it!
In conclusion, so much time has been dedicated on this Boeing market gap. I assume Boeing has spent more time and money on this concern. The lesson I have taken from the recent news articles is that Boeing's high priority things-to-do list now has a new member and its the 757 replacement.