I am very skeptical of all the claims of future efficiency gains based on the use of RNP and Continuous Descent profiles and all the other associated "NextGen" systems and concepts. Even today the vast majority of commercial airplanes flying have good RNP capabilities, but ATC cannot handle them by simply clearing them for a SID, route, STAR, and approach. There are so many vectors and altitude restrictions and speed constraints assigned that even a simple TOD calculation in an operative FMS is unlikely to be accurate by the time ATC gets done with it all.
I just don't see how a couple more/different boxes are going to make so much difference that all that vectoring and constraining is going to go away...