As you may know, many people do not know what the other molecule is beside fullerene in the ns9900 debut video. That molecule is known as a 'linked ball and chain dimer'. It is just fullerene molecules linked (strengthing the shaft and/or frame (whereever yonex wants to use it)) with each other. This is probably just for marketing purposes, just like the 'ultra pef' in the arcsaber 10. Personally, I think this molecule won't have too much use. Maybe this new molecule would make the racket more durable.

pictures: http://www.rsc.org/ej/IC/2000/b002947p/b002947p-f3.gif
http://www.rsc.org/ej/IC/2000/b002947p/b002947p-f4.gif
http://www.rsc.org/ej/IC/2000/b002947p/b002947p-f2.gif

Durability will probably be what the NS9.9K's new technology will be aimed at. Isn't that why they're making the 9900? More durability and more sales factor due to the new name.