If the 777X and 737 MAX are fitted with bleedless engines, this will require a lot of changes at least:
The ECS (environmental control system) will change which may cause the change of AC bay----> this may cause the change the wing-body fairings
The APU will change: no bleed air for aircraft/engines
The wings anti-ice will change ----->change in the slats
The electrical system may change: VFSG's instead of IDG's
All these changes mean extra costs in addition the cost of certification of these new systems.
I don't know if it is worth to fit bleedless engine in a new plane versus bleed air engine in new plane such B787 vs A350. But I don't think it is worth for derivative
planes such 737 MAX or 777X.
I agree for the 737 MAX - aside from the engines not a lot changed on the MAX relative to the NG. However the 777X barely qualifies as a derivative and more of an all new aircraft - new engines, new wings, new flight deck, nearly all new avionics, heavily revised fuselage - aside from the outside fuselage diameter there is precious little commonality between the 777 and the 777X. If going bleedless gave anywhere near the 3% fuel burn improvements that they thought they'd get for the 787, it would have made sense to go bleedless on the 777X. But it didn't, and they didn't.
As for the quoted 'advantages', note that was written over a year before the 787 actually flew - and most of that stuff didn't pan out. I already addressed the "more efficient engine cycle" and APU reliability is a laugh (the 787 APU has far and away the worst reliability of any Boeing installation). Sure, you get rid of bleed hardware, but you add lots of very heavy electrical hardware.
BTW, not positive, but memory says the 777X is getting rid of IDGs and going with VSCF architecture for electrical power generation.