Starting any conversation concerning the 797 has to begin with How much will it cost Boeing to Build the 797? The cost driver will locate the assembly point, design points and its suppliers. All which seem to reside near or in the USA. A mature infrastructure with trained engineers are required. A intact supply chain is a must. The big three happen to be in the Northwest corner of the US. Labor is the wild card for this project as the "Union" has a grip in Washington State. If the Union(s) can agree they will lock up the 797 for years to come. Boeing is waiting not on its customers to pull the 797 trigger but all is massive costly lose ends.
Most of those lose ends are already resolved but a significant element is the labor quotient. Automation is labor's undoing. Boeing is automating the 777X and has dialed in the the work force component with the 787 program. Boeing is figuring out how many workers it will need and how many machines can be positioned for the manufacturer of said product. The Unions are here to stay in Washington state but the numbers can be mitigated by new processes. When 10,000 workers were needed during 1950 only a 1,000 are need today for the same production output. Boeing hopes to reduce that number into the hundreds as machines drill holes and place fasteners in the process. Human hands are needed for stuffing and airplane body of all its wires, insulation and mechanical applications. Only time will give a complete snap together body connecting the parts which works into one snap. It will take only a few workers to finish the work in that future.
However, the 797 would only be half way there for a complete low cost high tech solution having precision beyond what a human can do. It just a matter of time before that happens. The 797 finds itself closing that gap because Boeing insist it will need to build 797 excellent enough and cheap enough at the same time. It will close the cost gap with plant, design and supplier innovation but it will need just enough people to build the 797. That is holding Boeing back until it figures the 797 costs component of the program.