I still simply don't see the capability gap where Boeing can put a twin-aisle $20 billion program into.
You have to think long term not short term. The next lot of engine upgrades will see the A350 and 787 near 10,000nm range. So the capability gap is growing.
The first 777 that flew only had a range 5,200nm.
The first A330 that flew only had a range of 5,300nm.
They both grew to 8000+nm monsters with multiple engine upgrades, aerodynamic upgrades, wingtips, MTOW increases. The same will happen with the 797.
Once the A330's range improved it started capturing more of the market from the 777 as it was lighter and could do 90% of the flights more efficiently. Today we see the 787 and A350 being lighter and more efficient than the 777X and the sales reflect this.
If the 797 starts as a smaller and more efficient widebody that can do 90% of the 787 and A350's current routes then we will see a repeat of history. The A321 could do 90% of what the 757 could do
Starting the 797 as a small very light widebody with modest range is the way to go. Every round of engine improvements will see the 797 gain market share and the 787 and A350 lose market share. We saw this with the 757 lose market completely to the more efficient lighter competition.
In 20 years time the 797 will probably fly 7000+nm with a premium cabin. It will feed the growing point to point market. Instead of feeding one large hub into another country an airline can send traffic to 3-4 cities. Look at the US west coast to Australia as a simplified example and compare 20 years ago to now.
Thinking long term hybrid electric will come for short haul aircraft. I expect the the 797 to replace the upper half of the 737 market and the lower half of the 787 market. The lower half of the 737 market which is mostly below 500nm will be replaced by some hybrid, electric style aircraft with 25+% efficiency improvement.