Post #728 is simply one person's speculation.
Speculation on this forum, be it about new rotorcraft or rotorcraft accidents, is open to reasoned rebuttal.
A short historical perspective:
Some of the more obvious improvements to the Advancing Blade Concept were presented in reports at the conclusion of the S-69 project. These consisted of; replacing the four engines with one, utilizing a pusher propeller, and significantly reducing the twist on the blades, etc.
At the time, some people were disappointed that the development was not continued. They believed that the ABC presented a unique and potentially viable way of providing rotorcraft with a meaningfully higher cruise speed. Later so did I, and therefore spent a few thousand hours researching, conceptualizing and developing potential methods of creating functional and practical solutions.
It eventually became apparent that my limited neuronal count was unable to find satisfactory answers to the concept's remaining limitations. However, I was willing to freely provide these ideas to others, on the Net and at an AHS convention, with the hope that they might 'spark' a better idea in others. I then moved on in search of other potential areas for VTOL improvement. Shortly thereafter, Sikorsky, with great fanfare, revived the thirty-year-old project.
Over time it became apparent that X2 was little more than a regurgitation of the old and that Sikorsky was not, in my opinion, addressing these meaningful limitations. At this point I began to question the motivation behind this 'project'.
If Sikorsky is has secretly developed one or more advancements, which overcome the ABC's limitations, AND the X2 was designed 'bolt-ready' to accept these advancements, I will sincerely apologize and eat crow.
Dave