Well, we can discuss VLA success theories forever but they will be out of production very soon.
Airbus announced A380 production cut starting 2018 to 12/year
Boeing claims large jet(all wide bodies) market is sluggish at best.
Boeing said is stretching 777X beyond 400+ is technically feasible.
There is no need knock out already down A380, so Boeing, just don't shoot yourself in the foot wasting few more $$$Billions on the stretch.
Both had a good run with large/very large wide bodies. Now concentrate on small planes 100-150 with 5000nm range. B737 MAX 7 is a good start.