Boeing
PR states the 777-9 will seat up to 407 passengers, close to 747 seat counts.
Deception.
Boeing uses "typical" seatcounts in this case 10 abreast in these new 777s.
BA tried and abandoned 10 abreast on the 777. Little chance they will re-use them next to the World Traveler seats currently used. E.g. the differences with the A380s would be too visible/ noticeable.
So use 9 abreast in the back and realize the 777-9 will be less then 3 meters longer then the A350-1000. Then look at both aircraft empty weights and the writing is on the wall IMO.