Well, not specifically for sounds, per se, but the fact that the Kronos contains 9 separate unique engines is pretty amazing, and the feature set is so rich that I can"t imaging mastering or leveraging it all in the next 10 years... this for tech which is already 9 years old.
I couldn"t justify the ~$3500 price tag for new, but I found a 'mint" (truly) K2 73 last October for nearly half that, and once acquired I quickly realized the value. I like the weighted action, but I also MIDI my TEX 61 for organ/synth lead use.
I ended up buying another 'mint" (truly) K2 88, again for about 1/2 retail, so that I could keep one in our rehearsal venue. I couple that one with my Triton LE 61.
My only real gripe is the weight - they are beastly if having to move from place to place very frequently (hence the second one).
From the inception of analog, through the FM evolution, ROMplers, etc... not sure there are a lot of areas where new unique soundforms can evolve. I personally believe that it is in form factors, methods of expression, and technical capability combinations where much of the future innovation lies. The technology will evolve, sure, just like the new MIDI standard which expands on the available addressing capability of the hardware, but I"m hard-pressed to think of any type of sound which can"t be generated by one technology or another today.